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Top intelligence officials struggled to explain to lawmakers Thursday why their initial talking points after the Libya attack minimized the role of militant groups, putting pressure on former CIA Director David Petraeus to set the record straight in another round of closed-door hearings Friday.

Lawmakers on the House and Senate intelligence committees heard testimony Thursday in private meetings with Director of National Intelligence James Clapper and Acting CIA Director Mike Morell. But Fox News was told there were heated exchanges on the House side, particularly over the talking points that administration officials relied on in the days after the Sept. 11 strike.

Fox News was told that neither Clapper nor Morell knew for sure who finalized that information. And they could not explain why they minimized the role of a regional Al Qaeda branch as well as the militant Ansar al-Sharia despite evidence of their involvement.

Further, Fox News was told Morell was pushed to explain why, during a Sept. 14 briefing, Petraeus seemed wedded to the explanation that the attack was in response to an anti-Islam video. Morell apparently said he wasn't at that briefing and had nothing further to add.

These lingering questions are sure to confront Petraeus when he visits Capitol Hill Friday morning to testify on Libya. The former director, after abruptly resigning last Friday over an extra-marital affair, agreed this week to testify anyway before House and Senate intelligence committee lawmakers.

As Petraeus prepares to face their questions, Republicans on another committee voiced mountain frustration with the administration's handling of the situation.

Lawmakers at a House Foreign Affairs Committee hearing Thursday sparred early and often, with Democrats accusing Republicans of turning a tragedy into a "political football" and Republicans accusing the administration of hiding the truth.

"This administration has lied to the American people about this tragedy," Rep. Dana Rohrabacher, R-Calif., said. "The arrogance and dishonesty in all of this is breathtaking. Let's not stonewall this issue and cover up mistakes, which seems to be what is going on today."

Lawmakers continue to express concerns on several fronts -- on whether warnings in the months preceding Sept. 11 were ignored, and on why the administration first insisted the attack was a "spontaneous" act.

U.S. Ambassador to the U.N. Susan Rice, who repeatedly said the attack was spontaneous on five Sunday shows after the attack, has been the focal point of that criticism. Obama, though, in his first post-election press conference Wednesday, called the criticism "outrageous" and told those lawmakers to "go after me" instead.

California Democratic Rep. Adam Schiff also came to Rice's defense Thursday, saying after the House intelligence committee hearing that Rice was given the intelligence community's "best assessment" at the time.

"Those who have suggested that Ambassador Rice was politicizing the intelligence or misrepresenting what the intelligence community was putting forward as its best assessment are either unfamiliar with the facts, or willfully disregarding them," he said.

Republicans, though, continue to criticize Rice and others in the administration for those comments.

Though Petraeus is embroiled in a scandal over an extramarital affair -- which led to his resignation -- he is not expected to address that when he speaks to lawmakers Friday. Rather, he will stick to Libya.

Lawmakers want to know, among other things, about a trip Petraeus took to Libya the week of Oct. 31. They are curious about a report that was put together summarizing his meetings and which may include details of his personal interviews with the CIA station chief in Benghazi about the attack. A State Department consulate, as well as a CIA annex, came under heavy fire that night.

Meanwhile, the affair scandal continued to reverberate through Washington.

Fox News confirms that the CIA is opening an "exploratory" investigation into Petraeus' conduct. The FBI and Justice Department have also faced scrutiny for sitting on the investigation for months.

Attorney General Eric Holder, though, on Thursday defended the decision to keep the probe under wraps until last week.

"We made the determination as we were going through the matter that there was not a threat to national security," he said. "Had we made the determination that a threat to national security existed, we would of course had made that known to the president and also to appropriate members on the Hill."

Fox News' Catherine Herridge contributed to this report.