By Will Stewart
Published: 15:21 EST, 16 May 2014 | Updated: 02:42 EST, 17 May 2014
Scientists are struggling to understand the cause of a 'sleeping epidemic' among the few remaining residents of a Russian Soviet-era 'ghost town' and a nearby village in Kazakhstan.
Dozens of locals in Krasnogorsk, Russia, and Kalachi, Kazakhstan, have been hit by the mystery condition which causes them to doze off for up to six days.
There are even fears one sufferer - an elderly man - was buried alive before the epidemic was diagnosed.
This is one of the victims of the 'sleeping epidemic' that routinely hits areas near a disused Soviet mine
An abandoned uranium mine in Krasnogorsk and the village of Kalachi is thought to be drugging residents
The illness has come in a number of waves, for example May 2013, New Year 2014, and this month.
Some residents even keep bags packed in case they need to be whisked to hospital.
It is believed to be caused by a disused uranium mine nearby - but experts cannot find evidence to make the connection.
Almost 7,000 experiments have been conducted into the mystery slumbers, with everything tested from local vodka to radiation, and including analyses of soil, water, air, blood, hair, and nails.
So far, all have come back inconclusive.
Children affected by the illness suffered serious and frightening hallucinations while weakness, drowsiness, dizziness and memory loss are also symptoms.
Adults simply blacked out.
Mystery: Dozens of locals doze off for up to six days, but scientists' tests have proved inconclusive
People, including this 75-year-old from Kalachi, Kazakhstan, pack hospital bags in case they are struck down
'I was milking cows, as usual, early in the morning, and fell asleep,' Marina Felk, 50, a milkmaid in Kalachi, told The Siberian Times.
'I remember nothing at all, only that when I came round I was in a hospital ward, and the nurses smiled and me, and said: "Welcome back sleeping princess, you've finally woken up".
'What else do I remember? Nothing. I slept for two days and two nights.
Krasnogorsk, which was once home to 6,500 people, has now become a ghost town and the remaining residents are struggling to make ends meet
A woman picks up logs in the quiet village of Krasnogorsk. Locals speculate that the problem arises after a sudden rise in temperature, but this has not been corroborated.
'The women in my ward said that I several times tried to wake up saying I needed to urgently milk my cows.'
Alexey Gom, 30, was struck down with the sleep plague when he visited relatives in Kalachi.
'I came with my wife to visit my mother-in-law,' he explained.
'I switched on my laptop, opened the pages that I needed to finish reading - and that was it.
Inconclusive: Almost 7,000 experiments have been conducted into the mystery slumbers, with everything tested from local vodka to radiation, and including analyses of soil, water, air, blood, hair, and nails
In the Soviet era, Krasnogorsk was a secret and 'closed' uranium mining town run directly from Moscow
Once 6,500 people lived in Krasnogorsk. Now it is only home to 130 who struggle for resources
Radiation danger signs are used to warn people as they approach the uranium mines
'It felt like somebody pressed a button to switch me off. I woke up in hospital, with my wife and mother-in-law by my bedside. The doctor found nothing wrong with me after a series of tests he performed.
'I slept for more than 30 hours.'
In the USSR era, Krasnogorsk was a secret and 'closed' uranium mining town run directly from Moscow.
Marina Felk, a milkmaid from Kalachi village, is pictured in hospital after being struck down with the 'sleeping epidemic'
A man from the Kalachi village is treated by doctors. Some residents are said to keep bags packed incase they are whisked to hospital
The hospital in Krasnogorsk, where many of the sufferers area treated. Most victims of the epidemic remember nothing from the days when they are struck down by the illness
The town was once home to 6,500 - now a mere 130 people live here, struggling to make ends meet.
Local community council head Alexander Rats said: 'You could find everything in our shops: meat, condensed milk, boots made in Yugoslavia - a miner could buy three new cars every year. We had two children's nurseries, both with swimming pools.'
Locals speculate that the problem arises after a sudden rise in temperature, but again this has not been corroborated.
Alexey Gom, 30, was struck down with the sleep plague when he visited relatives in Kalachi
He said it felt like someone had 'pressed a button' to switch him off, but doctors found nothing wrong after a series of tests
Some sufferers sleep for up to 30 hours once hit with the epidemic
While some scientists claim uranium gas evaporates from the mine, others claim it has seeped into local rivers.
It could be similar to the 'Bin Laden itch' in the USA when people found rashes on their skin because they were scared of possible bacteriological attack.
'Something like this often happens in closed communities,' he claimed.
Doctors have carried out extensive tests on sufferers but they cannot find a connection to the uranium
A statue of Lenin in the village of Kalachi. Some scientists claim the problem is caused in the village when uranium gas evaporates from the mine - others claim it has seeped into local rivers
Doctor-in-chief in nearby Esil, Kabdrashit Almagambetov, said: 'When the patient wakes up, he will remember nothing. The story is one and the same each time - weakness, slow reactions, then fast asleep.
'Sadly, the nature of this condition is still not known. We have excluded infections, we checked blood and spine liquid, nothing is there. We categorised it as toxic encephalopathy, but 'toxic' is just a guess here, and encephalopathy is just the title of the set of brain diseases.'
Radon gas is seen as a possible cause, but he is sceptical.
'I am an anaesthesiologist myself and we use similar gases for anaesthesia but the patients wake up a maximum in one hour after surgery,' he said.
'These people sleep for two to six days, so what is the concentration of this gas then? And why does one person fall asleep and somebody who lives with him does not?'