Classified hearings with survivors of the Sept. 11, 2012 terrorist attack in Benghazi, Libya, have further convinced at least some House Republicans that the investigation should continue.

President Obama insists no investigation is warranted into the attack that killed U.S. Ambassador Christopher Stevens and three others. Congressional Democrats have backed him. But House Republicans, including members of the House Intelligence Committee, said interviews with attack survivors only raised more questions about what happened that night.

The Intelligence Committee held its third closed-door hearing with surviving CIA contractors last week. Committee members are barred from commenting on classified information presented at closed hearings, but some lawmakers who spoke in broad terms about the investigation said the contractors' testimonies opened new lines of inquiry.

Among the top questions the committee wants answered is how involved Obama was in any decision not to dispatch military assistance to Benghazi. Republicans also want to know what the CIA was doing in Benghazi and why the agency had surviving security contractors sign nondisclosure agreements that legally barred them from discussing what happened.

Republicans are investigating why, in the immediate aftermath of the attack, the Obama administration failed to publicly acknowledgethat terrorists had attacked a U.S. diplomatic mission. The White House insists its early statements on the incident were based on erroneous initial reports that the violence was caused by Muslims upset over a U.S.-made video tape that mocked the Prophet Muhammad.

Rep. Lynn Westmoreland, R-Ga., chairman of the House Intelligence Subcommittee on Oversight and Investigations, told the Washington Examiner that the Benghazi inquiry is far from over.

“There are definitely things to look into,” Westmoreland said. “The thing that we have come realize is that [the survivors] knew, from their experience, that this was a coordinated attack. There was never any question about that. A couple of them were interviewed the day after the attack.”

The witnesses who testified shed no light on why military assistance was not dispatched to Benghazi once it was clear that a coordinated attack was underway. But the committee did learn from the CIA contractors that some of them were uneasy about the nondisclosure agreements they were told to sign while at the CIA ceremony honoring those killed.

“Some of them felt that it was out of the ordinary, others felt it wasn’t out of the ordinary. None of them felt pressured; they were never Benghazi specific,” Westmoreland said. “But at the same time, when you’re all invited to a gold star ceremony at CIA headquarters and you’re brought into a room together to sign a nondisclosure — at the same time, it just doesn’t smell right.”

Rep. Mike Conaway, R-Texas, chairman of the subcommittee on terrorism, HUMINT, analysis and counterintelligence, declined to discuss what he learned in the hearings about what happened that night. But he said the contractors' testimony did shed light on the attack itself.

“From the standpoint of what happened up until the State Department and the president began to mislead the American people on what happened," said Conaway, "I think we’re getting a very clear understanding of what happened that night in Benghazi.”