Testifying out of sight, Petraeus explained that references to terrorist groups suspected of carrying out the violence were removed from the public explanation of what caused the attack so as not to alert them that U.S. intelligence was on their trail, according to lawmakers who attended Petraeus' private briefings.
There have been many questions about the attack that killed a U.S. ambassador and three other Americans. Petraeus addressed the House and Senate intelligence committees in back-to-back, closed-door hearings.
The Obama administration initially blamed it on protests over an anti-Muslim movie. That story later shifted, raising questions about what the administration knew and when they knew it was actually a terrorist attack.
"Director Petraeus went to Tripoli. He interviewed many of the people, as I understand it, that were involved, and so the opportunity to get his views I think are very important," said Sen. Dianne Feinstein (D-Calif.).
The retired four-star general said initially, it was unclear whether the militants had infiltrated a demonstration to cover their attack.
Republicans remain critical of the administration's handling of the case. Sen. Marco Rubio, R-Fla., said Petraeus' testimony showed that "clearly the security measures were inadequate despite an overwhelming and growing amount of information that showed the area in Benghazi was dangerous, particularly on the night of Sept. 11."
In fact, Petraeus told lawmakers that protesters literally walked in and set fire to the facility, according to a congressional official who attended the briefing. U.S. Ambassador Chris Stevens died from smoke inhalation. Petraeus said security at the CIA annex was much better, but the attackers had armaments to get in.
Petraeus' testimony comes a week after he resigned because of an extramarital affair. The CIA has opened an exploratory investigation into Petraeus' conduct. Army officials said, at this point, there is no move to recall Petraeus to active duty in an effort to pursue adultery charges against him.
Lawmakers said Petraeus did not discuss his affair except to express regret about the circumstances of his departure and to say that Benghazi had nothing to do with his decision to resign.
More information is being revealed about the woman whose complaints triggered the FBI investigation into Petraeus' affair. According to a New York business man, Tampa socialte Jill Kelly allegedly used Petraeus' name to broker a contract for a $4 billion energy facility with senior officials of the South Korean government.
The Associated Press contributed to this report.