US officials said they suspect that that the attack at the Benghazi consulate, which had also been the target of an unsuccessful attack in June, may have been only tangentially related to the film.
They also stressed there had been no advance warning or intelligence to suggest a threat in Libya that would warrant boosting security, even on the 11th anniversary of 9/11.
As of Thursday morning, there was no intelligence indicating that what happened in Benghazi was planned, according to two US officials briefed on the investigation into the attack. Intelligence officials said they believe it's more likely that the attack was "opportunistic or spontaneous," with militants taking advantage of the demonstration to launch the assault.
There is also no evidence that the attack was tied to 9/11, one of the officials said. But the Libyan-based militant group Ansar al Sharia is the leading suspect for carrying out the violence, possibly with help from al Qaeda's main African-based offshoot, al Qaeda in the Islamic Maghreb. The officials said it may be hard to determine definitively which group was responsible, because many militants are members of both.
Libyan officials arrested an unspecified number of militants suspected of taking part in the attack and they were closely monitoring others to see whether they are linked to a group.
Eastern Libya has been home to a militant tradition for years. Hundreds of men from the region went to Iraq to fight Americans there. It was a recruiting ground for the now defunct Libyan Islamic Fighting Group too.