"Multiple" suspects are in custody connected to the deadly terrorist attack Sept. 11 on the U.S. Consulate in Benghazi, Libya, but U.S. access to the suspects so far been denied, an intelligence source tells Fox News.
"There are more suspects beyond those held in Tunisia and Egypt. Our access has been frustrated," the intelligence source said.
Since October, federal agents have sought access through the Tunisian authorities to Ali Harzi, who is thought to have played a role in the attack but is not considered a ring-leader.
Earlier this month, the Egyptians took Muhammad Jamal Abu Ahmad -- a former member of the Egyptian Islamic Jihad - into custody. In that case, Fox News is told, the U.S. access has been blocked even though Abu Ahmed admitted that he travelled to Libya specifically to assist in the training of the local extremist group Ansar al-Sharia in Benghazi.
Along with the Al Qaeda affiliate in north Africa, known as AQIM, Ansar al-Sharia is implicated in the coordinated commando-style consulate attack that killed four Americans, including Ambassador Chris Stevens.
The head of the House Intelligence Committee, Republican Rep. Mike Rogers, would not identify the countries holding the additional suspects, citing the sensitivity of the matter, but he confirmed that there are other suspects in custody and that federal agents are not getting the access they want.
"I will just say I'm very concerned about the lack of access to multiple people who have been taken into custody that could have ... strong information about the perpetrators of this event," Rogers told Fox News.
Democrat Rep. Adam Schiff, who also sits on House Intelligence, said the politicization of Benghazi had hampered the investigation, adding "across the spectrum there's more that needs to be done. But yes, we're still far from having a definitive picture to what degree there was any level of command and control, and who was responsible."
Fox News asked the FBI for comment, but there was no immediate response.
A State Department's security chief has resigned and three other officials could lose their jobs following the release this week of scathing report about safety lapses at the U.S. Consulate in Benghazi in the run-up to the terror attack.
The State Department-ordered investigation of the Sept. 11 attack on the consulate in Benghazi, Libya, concluded that "systemic failures" left the facility inadequately protected.
On Capitol Hill Friday, Sen. Lindsey Graham, R-S.C. suggested political differences between the U.S. and the Libyan government over who should lead the country may have been a motivating factor.
A Sept. 11 cable sent from Stevens to the State Department discussed how militias were warning the American government that if it backed prime minister candidate Mahmoud Jibril, it would risk losing viable security at the consulate.
“They criticized the USG for supporting National Forces Alliance (NFA) leader and Prime Minister candidate Mahmoud Jibril," the cable said. "If Jibril won, they said, they would not continue to guarantee security in Benghazi…"
Catherine Herridge is an award-winning Chief Intelligence correspondent for FOX News Channel (FNC) based in Washington, D.C. She covers intelligence, the Justice Department and the Department of Homeland Security. Herridge joined FNC in 1996 as a London-based correspondent.