A senior U.S. counterterrorism official has said that the September 11 attack on the U.S. consulate in Benghazi, Libya, was "a terrorist attack" but was most likely not planned in advance.
Speaking to members of Congress on September 19, the director of the U.S. National Counterterrorism Center, Matthew Olsen, said the incident was "an opportunistic attack" that "evolved and escalated over several hours."
"It appears that individuals who were certainly well-armed seized on the opportunity presented as the events unfolded that evening and into the morning hours of September 12th," he said.
He said there is no evidence yet of advance planning.
"We do know that a number of militants in the area as I mentioned are well-armed and maintain those arms," he said. "What we don't have at this point is specific intelligence that there was a significant advanced planning or coordination for this attack."
Olsen added that there are "indications" that some of the attackers had connections with Al-Qaeda.
"A number of different elements appear to have been involved in the attack, including individuals connected to militant groups that are prevalent in eastern Libya, particularly in the Benghazi area," Olsen said. " As well, 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."
Libyan officials have previously said they believe the attackers used a demonstration against the anti-Islamic film "The Innocence Of Muslims" as cover to carry out a pre-planned attack on the consulate.
U.S. Ambassador to Libya Chris Stevens and three other Americans were killed in the incident.
Last week, U.S. Attorney General Eric Holder announced that the FBI has opened a probe into the attack. FBI investigators are expected to arrive in Benghazi on September 21.
With reporting by Reuters, AFP, and Bloomberg