Intelligence sources tell Fox News they are convinced the deadly attack on the U.S. Consulate in Benghazi, Libya, was directly tied to Al Qaeda -- with a former Guantanamo detainee involved.

That revelation comes on the same day a top Obama administration official called last week's deadly assault a "terrorist attack" -- the first time the attack has been described that way by the administration after claims it had been a "spontaneous" act.

"Yes, they were killed in the course of a terrorist attack on our embassy," Matt Olsen, director of the National Counterterrorism Center, said during a Senate hearing Wednesday.

Olsen echoed administration colleagues in saying U.S. officials have no specific intelligence about "significant advanced planning or coordination" for the attack.

However, his statement goes beyond White House Press Secretary Jay Carney and Susan Rice, the U.S. ambassador to the United Nations, saying the Sept. 11 attack on the consulate was spontaneous. He is the first top administration official to call the strike an act of terrorism.

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Sufyan Ben Qumu is thought to have been involved and even may have led the attack, Fox News' intelligence sources said. Qumu, a Libyan, was released from the U.S. prison at Guantanamo Bay, Cuba, in 2007 and transferred into Libyan custody on the condition he be kept in jail. He was released by the Qaddafi regime as part of its reconciliation effort with Islamists in 2008.

His Guantanamo files also show he has ties to the financiers behind the Sept. 11 terrorist attacks. The declassified files also point to ties with the Libyan Islamic Fighting Group, a known Al Qaeda affiliate.

Olsen, repeating Wednesday that the FBI is handling the Benghazi investigation, also acknowledged the attack could lead back to Al Qaeda and its affiliates.

"We are looking at indications that individuals involved in the attack may have had connections to Al Qaeda or Al Qaeda's affiliates, in particular Al Qaeda in the Islamic Maghreb," he said at the Senate Homeland Security Committee hearing.

Still, Olsen said "the facts that we have now indicate that this was an opportunistic attack on our embassy, the attack began and evolved and escalated over several hours," Olsen said.

Carney said hours earlier that there still is "no evidence of a preplanned or pre-meditated attack," which occurred on the 11th anniversary of the 9/11 terror attacks.

"I made that clear last week, Ambassador Rice made that clear Sunday," Carney said at the daily White House press briefing.

Rice appeared on "Fox News Sunday" and four other morning talk shows to say the attack in Benghazi, Libya, that killed U.S. Ambassador Chris Stevens and three other Americans was "spontaneous" and sparked by an early protest that day outside the U.S. Embassy in Cairo, Egypt, over an anti-Islamic video.

"It was a reaction to a video that had nothing to do with the United States," Rice told Fox News. "The best information and the best assessment we have today is that this was not a pre-planned, pre-meditated attack. What happened initially was that it was a spontaneous reaction to what had just transpired in Cairo."

However, that account clashed with claims by the Libyan president that the attack was in fact premeditated. Other sources, including an intelligence source in Libya who spoke to Fox News, have echoed those claims. The intelligence source even said that, contrary to the suggestion by the Obama administration, there was no major protest in Benghazi before the deadly attack which killed four Americans. A U.S. official did not dispute the claim.

In the face of these conflicting accounts, Carney on Tuesday deferred to the ongoing investigation and opened the door to the possibility of other explanations.

Sen. Susan Collins, R-Maine, called Wednesday for an independent review of the attack.

"A State Department Accountability Review Board to look into the Benghazi attack is not sufficient," Collins said. "Given the loss of the lives of four Americans who were serving their country and the serious questions that have been raised about the security at our Consulate in Benghazi, it is imperative that a non-political, no-holds-barred examination be conducted."

Fox News' Bret Baier contributed to this report.