Faraj al-Shibli was last seen being detained by a local militia in Marj, Libya, two days ago, a Libyan source said.
Tripoli, Libya (CNN) -- A man once detained by Libyan officials and interviewed by the FBI over suspected links to the deadly 2012 attack on the U.S. diplomatic compound in Benghazi, Libya, has turned up dead.
Faraj al-Shibli, whose name is also spelled Chalabi, was last seen in the custody of a local militia in Marj two days ago, a Libyan source said. His body was found Monday in the eastern Libyan town.
He's the second Benghazi suspect to surface in recent weeks. U.S. forces arrested suspected attack mastermind Ahmed Abu Khattalah last month.
Here's what CNN has previously reported about those suspected of involvement in the attacks. With the exception of Abu Khattalah, it's unknown if any have been charged in connection with the Benghazi attack. The charges remain under seal.
Al-Shibli -- The Libyan government took al-Shibli into custody in March 2013 in connection with the Benghazi attack. The FBI was able to question him during that detention. Al-Shibli was no longer in custody as of May 2013, according to a Libyan source briefed on the case. Libyan officials have not explained why he was released. It's not clear what role he may have played in the attack, or if he's among the suspects named in sealed federal charges brought last year. Al-Shibli was a member of the Libyan Islamist Fighting Group, a militant organization that tried to overthrow the government of late Libyan leader Moammar Gadhafi in the mid-1990s. That regime named him as a suspect in the murder of a German counterintelligence official and his wife, who were killed in the Libyan town of Sirte in 1994. Libyan authorities also issued an arrest warrant for former al Qaeda leader Osama bin Laden in connection with the crime.
Abu Khattalah -- The Libyan militia leader for Ansar al-Sharia in Benghazi has been described as the mastermind of the attack -- an allegation he denied in an interview with CNN's Arwa Damon. He was captured by U.S. forces last month and brought to Washington to face charges. He has pleaded not guilty to one count of providing material support to terrorists and will remain jailed until his trial, a federal magistrate ruled July 2.
Ali Ani al Harzi -- Tunisian authorities held him in Tunis for several weeks in 2013 in connection with the Benghazi attack. A Tunisian judge released him in January on grounds of insufficient evidence, but a U.S. law enforcement official with direct knowledge of the Benghazi investigation told CNN at the time that al Harzi's release "doesn't mean he's any less a suspect."
Mohammed al-Zahawi -- One of the leaders in Ansar al-Sharia. He has denied the group's involvement in the attack, and U.S. officials have also expressed doubts.
Sheikh Nasser al-Tarshani -- Ansar al-Sharia's religious authority.
Sufian bin Qumu -- He headed the Darnah branch of Ansar al-Sharia, which the U.S. State Department said in January was involved in the Benghazi attack.
Several unnamed Yemeni men -- A senior law enforcement source told CNN in May 2013 that authorities had traced the men to northern Mali, where they are believed to have connected with a fighting group commanded by jihadist leader Moktar Belmoktar. It's unclear where these men might be.
Moktar Belmoktar -- He is an Algerian terror suspect linked to al Qaeda in the Islamic Maghreb who was on the receiving end of an excited phone call from someone in or close to Benghazi in the attack's aftermath, a source briefed on the investigation told CNN in May 2013. "Mabruk, Mabruk!" the caller repeated, meaning "Congratulations" in Arabic. There is no proof the call was about the attack, but it was assumed to be, the source said. Troops in Chad claimed to have killed Belmoktar in 2013, but several taped messages from him have been released since then.
Mohammed Jamal Abu Ahmed -- According to a U.S. official with direct knowledge of the investigation, authorities were examining in December whether Abu Ahmed played a role in the attack. He is allegedly the leader of a post-revolution terrorist network in Egypt. He was released from jail after the downfall of Egyptian President Hosni Mubarak but was thought to be back in an Egyptian prison late last year.
CNN's Jomana Karadsheh reported from Libya; CNN's Holly Yan and Mike Pearson wrote from Atlanta. CNN's Susan Candiotti, Paul Cruickshank, Tim Lister, Nic Robertson and Fran Townsend contributed to this report.