The film's director, who called himself Sam Bacile and said Tuesday he is American-Israeli and had Jewish financial backing, went into hiding after the protests in Egypt and Libya over his low-budget movie "Innocence of Muslims."
But doubts about his identity grew, culminating in US media reports pointing to a California Coptic Christian convicted of financial crimes, living outside Los Angeles.
Adding further to the puzzle, the cast and crew of the movie voiced anger at having been exploited, with at least one saying that offensive parts of dialogue had been dubbed over their own words, as filmed.
US ambassador to Libya Chris Stevens and three other Americans were killed in Benghazi, Libya on Tuesday, the 11th anniversary of the September 11, 2001 attacks on the United States.
Steve Klein, a consultant on the movie, denied that Israeli authorities were involved in the film, and said Bacile -- which he acknowledged was a pseudonym -- was mortified to hear of the US ambassador's death.
"He's very upset that the ambassador got murdered," he told AFP.
In a Wall Street Journal interview published Tuesday, "Bacile" took straight aim at Islam.
He said that he had raised $5 million to make the movie from about 100 Jewish donors, and used some 60 actors and 45 crew to make the two-hour movie in a three-month period last year in California.
The film was screened in one Hollywood movie theater about three months ago, and sank without trace, until an Arabic-language dubbed version was released last week and footage was aired by an Egyptian TV station, triggering protests.
But the cast and crew voiced anger Wednesday, according to CNN, which cited a joint statement as saying: "The entire cast and crew are extremely upset and feel taken advantage of by the producer.
"We are 100% not behind this film and were grossly misled about its intent and purpose... We are shocked by the drastic re-writes of the script and lies that were told to all involved.
Actress Cindy Lee Garcia, who plays a woman of a young daughter said she did not know the film was anti-Muslim propaganda, adding that dialogue had been overdubbed after filming.
"It was going to be a film based on how things were 2,000 years ago," Garcia told the gossip website Gawker. "There wasn't anything about Mohammed or Muslims or anything."
Indeed, the over-dubbing of dialogue is obvious to even to a casual viewer of a 14-minute clip for the movie available online, with words crudely inserted in the middle of sentences.
Online reports cited in the New York Times blog suggested Morris Sadek, an Egyptian-born Coptic Christian, and his ally Terry Jones, the Florida pastor notorious for previous Koran-burning stunts, had cooperated in promoting the movie.
But later Wednesday a report cited by US media identified Nakoula Basseley Nakoula as saying he managed the company that produced the film, and that he was a Coptic Christian.
The 55-year-old, who was sentenced to 21 months in jail over federal bank fraud charges in 2010, denied however that he was Sam Bacile, even though a cellphone used for a media interview Tuesday was traced to his address.
Klein said he did not know the filmmaker's nationality -- and denied that Israeli authorities had anything to do with the project.
"I know there's some rumors out there, that Israel did it. No. Israel's not involved... This was private people, private money."
Klein warned that the director could suffer the same fate as Dutch filmmaker Theo Van Gogh, who was assassinated in 2004 after triggering protests with an anti-Muslim film.
"He could get killed, really easily," he said.
Pastor Jones meanwhile denied that the film was against Muslims. "The film is not intended to insult the Muslim community, but... to reveal truths about Mohammed that are possibly not widely known," he said in a statement.
"The fruits of the religion speak for themselves. For example the recent outbreak of violence and deaths is not because of the film, it is not because of the activities that we have done, and that we will continue to do."
The top US military officer, General Martin Dempsey, called Jones, whose previous threats to burn the Koran ignited deadly riots in Afghanistan, to urge him to disavow the film.