Image caption Media crews arrived at Nakoula's house in the early hours

US police have visited the home of a California resident who admitted involvement in the film which sparked anti-US riots in the Arab world.

Nakoula Basseley Nakoula, 55, of Cerritos, California, is said to be a Coptic Christian of Egyptian origin.

He told the Associated Press on Wednesday that he was the manager for the company that produced the film.

But he has denied being "Sam Bacile", credited as the writer and director of the film.

However, the Associated Press says police now believe Mr Nakoula was in fact the director of Innocence of Muslims.

Police were photographed entering and leaving Mr Nakoula's house on Wednesday night.

The front door of the property is said to resemble a door used in the controversial film.

Sam said no this is not your fault. He said, you tell the world that I did this. That I wrote this script Cindy Lee Garcia, Actor

A spokesman for the sheriff's department in Cerritos refused to confirm Mr Nakoula's link to the film, telling the BBC: "All we are doing is providing safety for anybody that needs it."

The obscure film mocked Muslims and the Prophet Muhammad. It was shown to tiny audiences in Los Angeles in June, but has since achieved notoriety online.

A clip of the film dubbed into Arabic has been blamed for sparking protests at US missions in Egypt, Libya, and Yemen.

US Ambassador J Christopher Stevens and three other Americans died in an attack on the diplomatic mission in Benghazi, Libya.

Unconfirmed reports suggest the Libya attack could have been planned ahead of the appearance of the film.

Mystery film

The exact origin of the film and the internet clip, and the motivation behind its production, remains a mystery.

A man saying he was the writer and director, and claiming to be called Sam Bacile, spoke to a number of media outlets on Tuesday, making inflammatory anti-Islamic comments in support of the film.

He claimed to be 52, or 56, depending on the source, and to be an Israeli-born Jewish estate agent.

Media playback is unsupported on your device Media caption US Secretary of State Hillary Clinton described the video as "reprehensible"

The most offensive comments about Islam and the Prophet Muhammad had been quite obviously dubbed onto the soundtrack afterwards and not spoken by the actors, the BBC's Alastair Leithead reports.

Cindy Lee Garcia, from Bakersfield in California, was quoted by the website Gawker saying she had a small role in a film which she was told would be called Desert Warriors, about life in Egypt 2,000 years ago.

She threatened to sue the director for the way the actors were represented.

"I said why did you do this, why did you do this to us Sam," she told CBS on Wednesday. "He said no this is not your fault. He said, you tell the world that I did this. That I wrote this script."

The extent of any involvement by Mr Nakoula in the film's production is not yet clear.

However, court documents related to a criminal prosecution in 2010 show him using aliases including Nicola Bacily, Robert Bacily and Erwin Salameh.

He pleaded no contest to federal bank fraud charges in California. US prosecutors said he set up fraudulent bank accounts using stolen identifies and Social Security numbers.

In addition to restitution and 21 months in federal prison, Mr Nakoula was ordered not to use computers or the internet for five years without approval from his probation officer, AP reported.