The Manchester Arena bomber could have been blown up by other members of his terror cell using a remote controlled explosive, it has emerged.
Salman Abedi killed 22 and injured around 120 people when a bomb he was carrying in a rucksack exploded as families flooded out of an Ariana Grande concert on Monday evening.
But analysis of pictures of bomb parts leaked by US officials suggests the device may have been remotely detonated by a member of a potential network thought to have made the explosive.
Pictures of the bomb site leaked by US law enforces suggest there may have been two detonators on the bomb, one handheld and another remotely operated.
Former army officer Hamish de Bretton-Gordon said photos of the bomb suggested Abedi had 'significant help', adding: 'This is not something you can knock up in your back shed.'
Mr de Bretton-Gordon, now director of Avon Protection Systems, told MailOnline: 'I would suspect that they didn't have confidence he was going to go through with it. He might not even have known that it had a remote detonator or that they could blow him up themselves.'
Suicide bomber Salman Abedi carried the explosive in a metal container, believed to have been in a Karrimor backpack
Investigators found a destroyed 12-volt lead acid battery (pictured) after the attack in Manchester Arena, suggesting measures were taken to make sure the bomb didn't fail. It is thought the bomb was made by a professional
Pictured: The bomb's detonator. The sophistication of the device suggests it was probably not made by Abedi himself
ISIS, who have claimed responsibility for the attack, have previously used remote controlled bombs to execute prisoners in Syria.
The Manchester bomb, which was packed in a £20 Karrimor backpack, is one of the most sophisticated set off in Britain since attacks by the IRA.
Pictures of pieces of the device, first published by the New York Times, emerged just hours after the UK Government issued a warning to US authorities not to release details of the terror investigation.
The newspaper reported that screws and shrapnel dispersed by the bomb were found deeply embedded in brick walls and metal doors, suggesting a very powerful blast.
Also leaked was a diagram showing the location of the bodies of those killed. The fact that they were found in a circle around where the bomb is believed to have gone off suggests the bomb was evenly-packed, experts say.
Photos of bloodstained fragments of the device show a piece of the bag which contained the bomb, the detonator and some of the nails and screws packed around it to cause maximum injury to young music fans and their parents.
The leaked photos show the remains of a small detonator used to explode the bomb, which security specialists think is similar in design to those used in attack on Brussels last year.
A 12-volt lead acid battery found at the scene suggest the makers were careful to reduce the risk of it not going off, experts say. It is more powerful than most seen in backpack bombs or suicide vests and is commonly used for emergency lighting.
Circuit boards found at the scene suggest the makers may have included a fail-safe mechanism, allowing it to be detonated remotely if not set off by Abedi.
Salman Abedi (pictured left and right) is believed to have returned from war-torn Libya before launching his horrific attack
Nails, bolts and screws were packed around the explosive to inflict maximum injuries in the busy foyer area of the arena
Shocking pictures released to US media show pieces of shrapnel on the floor of the foyer area where 22 people were killed
A diagram of where 16 victims' bodies were found has also been leaked. That victims were found on all sides of the bomb blast suggests it was made by experts. The suicide bombers torso is understood to have been some distance from the blast. It is unclear where the rest of the victims were found
The care and attention with which the bomb was made has fuelled suggestions that Abedi worked with a skilled bomb maker or team of bomb makers, who are feared to still be on the loose.
The location of the Abedi's torso, and the absence of fatalities in a line between the blast site and where he landed, indicated that the bomb was most likely in a backpack rather than a vest, an explosive disposal technician who examined the images said.
CCTV stills, taken in Manchester's Arndale Centre, allegedly show Abedi with a rucksack, similar to the one used in the bombing, just three says before the attack.
Sky News reported that the man took £250 from a cash machine and then went shopping in the Arndale Centre at about 8pm on Friday.
Armed police carried out a series of raids today, believed to be a hunt for the bomb factory.
Eight people remain in custody in connection with Monday's attack. Armed police today chased and arrested a man in Nuneaton, Warwickshire and bomb disposal experts rushed to the Hulme area of Manchester, where armed officers pinned a man to the floor. The home of a man arrested in Wigan yesterday is also being searched.
The release of the photos comes after previous leaks by US authorities infuriated Home Secretary Amber Rudd, who said on Wednesday she was 'irritated' by the early release of the bomber's name in the US.
Found on the bloodied floor of Manchester Arena was a detonator (pictured), shrapnel and a battery
Investigators were not able to specify the exact size or type of the bomb during initial investigations
This is believed to be a battery used in the bomb. It has been suggested the device may have been set of remotely
CCTV (left and right) taken in Manchester's Arndale Centre allegedly shows Salman Abedi shopping just three days before he blew himself up after an Ariana Grande concert. The thin man, wearing trainers and a baseball cap, was caught on camera on Friday night
It was reported this morning that UK police have stopped sharing information with US law enforcers in the wake of the leaks.
US President Donald Trump Thursday slammed as 'deeply troubling' US leaks on the probe into the Manchester suicide bombing, warning those responsible could face prosecution.
In a statement issued by the White House, Trump said he had ordered the Department of Justice and other agencies to launch a full review of leaks he described as 'a grave threat to our national security.'
'The alleged leaks coming out of government agencies are deeply troubling,' Trump said. 'If appropriate, the culprit should be prosecuted to the fullest extent of the law.'
'There is no relationship we cherish more than the Special Relationship between the United States and the United Kingdom,' Trump added.
Security agencies and detectives investigating the suicide bombing regard the ability to control the release of information as crucial to the success of their operation.
It is understood police wanted to keep Abedi's name secret for longer to help them with their investigation.
The scene in Nuneaton as police with Taser and firearms drawn arrest a man after chasing him for nearly half a mile
Armed police point a gun at the head of a man in the Hulme area of Manchester during a bomb scare in a street near a school
Abedi's name was circulating in the US media on Tuesday, hours before it was confirmed by UK police who had urged reporters not to publish speculation about the bomber's identity.
Britain's intelligence links with the US are among the closest in the world.
Information is routinely shared by security and intelligence agencies as part of the special relationship between the transatlantic allies and surveillance information is also shared between the UK, US, Canada, Australia and New Zealand under the 'Five Eyes' arrangement.
Voicing her concern about the apparent release of information to the US press, Ms Rudd told the BBC: 'I have been very clear with our friends that that should not happen again.'
The Home Secretary said it was 'irritating' when information was released from other sources as British authorities worked on the ongoing investigation.
However she added that she did not believe that the Americans had compromised the investigation.
British-born Abedi killed 22 people and injured at least 119 more when he detonated his bomb as children were piling out of the venue having watched American pop star Ariana Grande.
The mass-murderer had only just returned from a three-week trip to war-torn Libya before launching his horrifying attack, friends said. He is believed to have been in Germany just days before the attack.
The publication of the photos will infuriate Home Secretary Amber Rudd (pictured), who said on Wednesday she was 'irritated' by the early release of the bomber's name by US authorities
Ramadan Abedi (pictured) the father of Manchester Arena bomber Salman Abedi claims his son seemed 'normal' when they last spoke five days ago. He was later arrested in Tripoli
Ramadan Albedi also published a picture of his son Hashem holding a machine gun while wearing a Nike t-shirt and combat trousers. Underneath the picture he wrote: 'The lion Hashem... is training'
British ministers have voiced their fury to American counterparts after photographs showing the bloodstained Manchester Arena were leaked in the US.
The disclosure is regarded as 'completely unacceptable' by Britain, because of the risk it could complicate ongoing investigations into the atrocity.
A Whitehall source said: 'We are furious. This is completely unacceptable. These images leaked from inside the US system will be distressing for victims, their families and the wider public.
'The issue is being raised at every relevant level by the British authorities with their US counterparts.'
The National Police Chiefs' Council said the 'unauthorised disclosure of potential evidence' to US media about the Manchester bombing investigation 'undermines our investigations and the confidence of victims, witnesses and their families.'
Abedi's younger brother Hashem has also been arrested in Tripoli, Libya, on suspicion of having links to ISIS who claimed responsibility for Monday night's atrocity.
He was 'aware of all the details' of his brother's plans, a Libyan security force official said and had been 'under surveillance for a month and a half' before his arrest today.
The Deterrence Force said on its Facebook page that 'investigation teams supplied intelligence that he was planning a terrorist attack in the capital Tripoli'.
Abedi's older brother Ismail, 23, was arrested yesterday in Chorlton, south Manchester.
He is still being quizzed by police, who are probing the family's links to a terror network.
Manchester's police chief said it is 'very clear' that police are investigating 'a network' linked to the bomber.
Detectives, in tandem with British soldiers, have carried out several raids since Monday night's atrocity.
By Wednesday night nine people had been arrested, including Albedi's father and younger brother in Tripoli, his older brother in Manchester and a woman in Blackley.
Forces had carried out raids at locations in Manchester, Wigan and Nuneaton in an anti-terror operation.
Former Libyan security official, Abdel-Basit Haroun, said Ramadan Abedi, a former airport security worker, was a member of the Libyan Islamic Fighting Group (LIFG) in the 1990s. The organisation had links to Al-Qaeda.
Exclusive pictures show Salman Abedi (circled) as an innocent schoolboy, seven years before he murdered 22 people including children as young as eight. There is a no suggestion any of the friends he is pictured with have been involved in any wrong doing
Although the LIFG disbanded, Haroun said the father belonged to the Salafi Jihadi movement, the most extreme sect of Salafism from which Al-Qaeda and ISIS hail.
Ramadan Albedi has also publicly voiced his support for an extremist group fighting in Syria. He posted photos of soldiers clad in black uniforms from the Al-Nusra Front, which was the official Syrian branch of al Qaeda until it broke up last July, on his Facebook page five years ago.
Underneath the photo, he wrote: 'Victorious against the infidels... say Amen!'
Ramadan Albedi also published a picture of his son Hashem holding a machine gun while wearing a Nike t-shirt and combat trousers. Underneath the picture he wrote: 'The lion Hashem... is training'.
Investigation: Scenes of crime officers wearing white suits were working close to the scene of the attack this morning
Over the past 48 hours, raids have been carried out at locations in Manchester, Wigan and Nuneaton in an operation following Monday's horrific terror attack
Theresa May (pictured) has said the terror threat level has been raised to 'critical' for the first time since 2007
Troops were deployed onto Britain's streets amid fears a further terror attack 'may be imminent', the Prime Minister announced.
The Prime Minister confirmed the identity of the Manchester suicide bomber as 22-year-old Salman Abedi, a Mancunian of Libyan descent.
But intelligence agencies fear he may not have acted alone - leaving open the possibility of an active Islamist terror cell on the loose.
Britain's Joint Terrorism Analysis Centre last night raised the terror threat level to 'critical', its highest level.
The threat level has only been raised to 'critical' twice since the system was introduced on August 1, 2006.
Speaking inside Downing Street following a meeting of the emergency committee Cobra, Mrs May said: 'Earlier today I said the security services needed to investigate whether Abedi was working alone and these investigations continue.
'It is a possibility we cannot ignore that there is a wider group of individuals linked to this attack.
'The joint terrorist analysis centre has concluded that the threat level should be increased for the time being from severe to critical.
'This means that their assessment is not only that an attack remains highly likely but a further attack is imminent.'
It means armed soldiers will patrol key sites across the country, at sporting fixtures and musical events.
Undercover SAS troopers will join regular soldiers in Operation Temperer.
Manchester Arena braced for the performance of Ariana Grande
6pm: Doors open at Manchester Arena in the north of the city centre. US pop singer Ariana Grande is on the bill for a sell-out concert. Fans, many of them teenage girls, excitedly share selfies as they wait for the show to begin. The 21,000-capacity venue, which is the biggest indoor arena in the UK and the second larges in Europe, was sold out.
7.30pm: The show gets underway with a support act BIA, an American rapper, taking the stage. Fans wait patiently for the main event - American superstar Ariana Grande.
9pm: Ariana Grande arrives on stage to the delight of the thousands of fans who have travelled the globe to watch her perform her hits which include Problem, Bang Bang and Break Free.
10.30pm: The star leaves the show and thousands of gleeful fans begin to file out of the arena's four exits. With the huge venue only half-empty, the horrifying sound of the booming bomb reverberates around the arena. Witnesses describe being knocked from their feet by an explosion and seeing dozens of injured, possibly dead, people including children lying on the floor. Others describe panic as concert-goers run for exits.
10.33pm: Greater Manchester Police (GMP) are called to reports of an explosion at Manchester Arena. Dozens of emergency services vehicles stream into the area and the emergency is confirmed two minutes later.
10.46pm: The North West Ambulance Service are called to the scene. They send 60 ambulances to Manchester Arena where victims have been maimed with shrapnel including nails and metal nuts from a bomb.
This photo shows the aftermath of the suicide bomb which ripped through the foyer of the venue killing parents and children
The bomber is believed to have entered a foyer area of the venue through doors opened to allow young music fans to leave
10.55pm: Police urge people to stay away from the area as responders deal with a 'serious incident'. A huge police cordon is set up surrounding the building and roads are closed to the public as fans flee the massacre.
11.46pm: Police confirm there have been a number fatalities, but cannot confirm the figure.
1.10am: Nineteen people are confirmed dead and around 50 others injured following the suspected explosion police say is being treated as a terrorist incident.
1.35am: A controlled explosion is carried out on a suspicious item in the Cathedral Gardens area near Manchester Arena. It is later confirmed to be abandoned clothing.
Bloodied concertgoers were pictured being helped by armed police outside the arena after explosions rang out at the gig
2.15am: Prime Minister Theresa May says her thoughts are with the victims and families of those affected in 'what is being treated by the police as an appalling terrorist attack'.
3.51am: Shortly before 4am Ariana Grande tweets that she is 'broken', adding: 'From the bottom of my heart, I am so so sorry.'
7am: GMP Chief Constable Ian Hopkins gives a statement. He says the death toll has risen to 22, including children, with 59 injured. He confirms police are treating the attack as a terrorist incident and believe it was carried out by a suicide bomber detonating an improvised explosive device.
9.02am: US President Donald Trump expresses his 'deepest condolences' and calls those responsible 'evil losers'.
9.30am: The first victim of the atrocity is named as Georgina Callander. Miss Callander, 18, had posted a picture of herself with Ariana Grande at the same venue two years ago, captioning it: 'My meet and greet photos came through, she was so cute and lovely, I hugged her so tight and she said she loved my bow. I can't get over this, I never will.'
10.30am: GMP says it has arrested a 23-year-old man in South Manchester in connection with the incident. Footage shows officers leading the handcuffed 23-year-old to a police van outside a Morrisons supermarket in Chorlton-Cum-Hardy, south Manchester at about 10.30am this morning. Witnesses said the man was ordered to 'get on the ground' and that he was seen smiling at one point as a team of officers, who had arrived in a black Mercedes, made the arrest.
Armed officers arrested a man in south Manchester today with police saying the action was linked to the attack
11am: After chairing a Cobra meeting, Mrs May says the attacker has been identified by security services, but does not release details. She says the 'callous' attack was 'among the worst terrorism we have experienced in the United Kingdom'.
11.30am: The ambulance service confirm the number of people injured has reached at least 119. Of those hurt, 59 were taken to eight different hospitals in the Manchester area while around 60 were treated at the scene as walking wounded. The trust's chief executive Derek Cartwright admitted nothing could prepare his staff for a moment like this.
12.12pm: The Queen releases a statement expressing her 'deepest sympathy' to all those affected by the explosion, adding that the whole nation had been shocked by the 'death and injury'.
12.41pm : Islamic State claims responsibility for the atrocity. The extremists were quick to call the killer one of their soldiers, as has become the trend in the wake of many recent attacks in Europe. According to the SITE Intel Group, which monitors jihadist groups, the IS statement described the explosion as having taken place at a 'shameless concert arena'.
Eight-year-old Saffie Rose Roussos (left), 18-year-old Georgina Callander (right) and 26-year-old John Atkinson have been named as three of the 22 victims of the suicide bombing. It is feared many children are among those killed, as well as parents who had accompanied their youngsters to the concert or were picking them up
1.37pm: Saffie Roussos, 8, is confirmed as the youngest named victim of the terror attack. She has been described as 'simply beautiful'. Chris Upton, the headteacher of her school, Tarleton Community Primary, said: 'The thought that anyone could go out to a concert and not come home is heartbreaking.' Minutes later, the third victim was named - 26-year-old John Atkinson from Radcliffe who was leaving the concert. Friends and family have paid their respects online, describing him as an 'amazing young man'.
2.02pm: GMP say they have executed warrants at addresses in Whalley Range, and one in Fallowfield where they carried out a controlled explosion.
4.30pm : Attacker named as Salman Abedi. Abedi, a 23-year-old British man of Libyan origin, detonated a deadly explosive that ripped through crowds leaving an Ariana Grande concert at 10.30pm. Police are trying to determine whether Abedi acted alone or was part of a wider terror cell.