A US law enforcement official says a man named Nakoula Basseley Nakoula is behind the anti-Muslim film that has sparked mob attacks on US missions in Egypt, Libya and Yemen.
A man who calls himself Sam Bacile has said he created the film, but The Associated Press has connected Nakoula to the Bacile persona.
The official spoke on condition of anonymity because he was not authorised to discuss an ongoing investigation.
The self-proclaimed director of Innocence of Muslims initially claimed a Jewish and Israeli background. But others involved in the film said his statements were contrived as evidence mounted that the film's key player was a southern Californian Coptic Christian.
Nakoula, 55, told The Associated Press in an interview outside Los Angeles on Wednesday that he managed logistics for the company that produced the film.
He denied he had directed the film, though he said he knew the self-described filmmaker, Sam Bacile. But the mobile phone number that the AP contacted on Tuesday to reach the filmmaker who identified himself as Bacile traced to the same address near Los Angeles at which Nakoula was located.
Nakoula told the AP he is a Coptic Christian and supported the concerns of Christian Copts about their treatment by Muslims.
The film was implicated in protests that resulted in the burning of the US consulate in the eastern Libyan city of Benghazi on Tuesday.
Libyan officials said ambassador Chris Stevens and three other embassy employees were killed during the mob violence, but US officials now say they are investigating whether the assault was a planned terrorist strike linked to Tuesday's 11th anniversary of the September 11 terrorist attacks.
Nakoula denied he had posed as Bacile. Federal court papers filed in a 2010 criminal prosecution against him said Nakoula had used numerous aliases in the past. Among the fake names, the documents said, were Nicola Bacily and Erwin Salameh.
During a conversation outside his home, Nakoula offered his driver's licence to show his identity but kept his thumb over his middle name, Basseley.
Records checks by the AP subsequently found that middle name as well as other connections to the Bacile persona.
Film disgusting: Clinton
US Secretary of State Hillary Clinton has condemned the film, stressing the US government had nothing to do with it.
"To us, to me, personally, this video is disgusting and reprehensible. It appears to have a deeply cynical purpose, to denigrate a great religion and to provoke rage," Mrs Clinton said on Thursday.
"But as I said yesterday, there is no justification, none at all, for responding to this video with violence."
Condemning the violence, Mrs Clinton said at the launch of a strategic dialogue between the United States and Morocco that all "leaders in government, leaders in civil society or religious leaders must draw the line at violence".
"Any responsible leader should be standing up now and drawing that line," she added.
"It is especially wrong for violence to be directed against diplomatic missions. These are places whose very purpose is peaceful to promote better understanding across countries and cultures."