(CNN) -- American authorities are examining whether the leader of a post-revolution terror network in Egypt played a role in the September 11 attack on the U.S. Consulate in Benghazi, Libya, according to a U.S. official with direct knowledge of the investigation.
Muhamed Jamal Abu Ahmed has been detained by Egyptian authorities; however, the FBI has not yet had access to him, the official said.
Asking not to be identified because of the sensitivity of the case, the official says Abu Ahmed came to authorities' attention after the attack and has remained there for "a long time."
The source would not comment on what led to Abu Ahmed or on any possible intelligence shared between the United States and Egypt, but an Egyptian security official told CNN there was cooperation between U.S. government officials and Egyptian security authorities.
Abu Ahmed, a well-known jihadist, was released from jail after the downfall of Egyptian President Hosni Mubarak. He's believed to be the driving force behind a new terror group seeking to align with al Qaeda, the two officials said.
He was arrested by security forces in the province of Sharkia two weeks ago in a house rented under a different name, according to an Egyptian security official. He had two machine guns, ammunition and a laptop. His temporary detention has been extended to 15 days for further investigation.
He admitted that he had traveled to Libya several times during the revolution there and joined the resistance but denied any connection to the attack on the consulate or affiliation with al Qaeda, the Egyptian official said.
Egyptian intelligence officers believe he has an affiliation with a terrorist cell in Cairo's upper-class Nasr City, where five suspected terrorists were captured after a fierce gun battle with security forces in October. The cell became known as the Nasr City cell.
Explosive belts, rocket-propelled grenades, machine guns, hand grenades, rockets and ammunition were found in the flat when the five suspects were arrested.
The cell is accused of planning to blow up government buildings, the Interior Ministry and embassies and to assassinate high-profile political figures, according to their statements to authorities and information retrieved from their laptops. They are also accused of unspecified connections to the Benghazi embassy attack.
Muhamed Jamal Abu Ahmed and the five suspects will face trial in a security court soon.
Abu Ahmed, 45, who holds a master's degree in sharia law, was imprisoned during the Mubarak era on charges of "conspiring to topple the regime," but was not convicted. He was released from prison after uprisings began on January 25, 2011, and eventually toppled Mubarak. He speaks English, stands about 5-foot-7 and maintains a thick beard.
But the U.S. government suspects he may have led a terrorist ring in Libya and provided training and funding for them before ordering them to attack the U.S. Consulate. He denies such charges and claims he was fighting alongside the rebels in Libya.
Most of the weapons retrieved in the Nasr City flat are not new in Egypt, but the rockets and explosive belts alarmed the security officials. An influx of weapons arrived mainly from Libya and Sudan during the security vacuum that followed the uprising.
Meantime, another possible suspect, Tunisian Ali Ani al Harzi, remains detained in Tunisia. He was picked up in Turkey following the attack on the U.S. Consulate.
After weeks of attempting to gain access to al Harzi, the FBI finally met with him in the presence of Tunisian authorities. However, al Harzi refused to talk with American investigators, according to the U.S. official.
CNN's Tim Lister contributed to this report.