Libyan authorities have made four arrests in the investigation into the attack on the US consulate in Benghazi in which the US ambassador and three embassy staff were killed, the deputy interior minister said on Thursday. "Four men are in custody and we are interrogating them because they are suspected of helping instigate the events at the US consulate," Wanis Sharif told Reuters. Related articles: Obama: Egypt not an ally or enemy Clinton: US had nothing to do with film MK: Zionists to blame for anti-Islam film US ambassador to Libya Christopher Stevens and three other Americans died after the gunmen attacked the US consulate and a safe house refuge in the eastern city of Benghazi on Tuesday night. The attackers were part of a mob blaming America for a film they said insulted the Prophet Mohammad. US consulate after attack (Photo: AFP) Sharif said the attack was an organized two-part operation by heavily armed militants that included a precisely timed raid on a supposedly secret safe house just as Libyan and US security forces were arriving to rescue evacuated consulate staff. The attacks were suspected to have been timed to mark the 9/11 anniversary and that the militants used civilians protesting an anti-Islam film as cover for their action. Infiltrators within the security forces may have tipped off militants to the safe house location, he said. Attack on US Consulate (Video: Reuters) Sharif gave The Associated Press an account of the night's chaotic events. The crowd built at the consulate - a one-story villa surrounded by a large garden in an upscale Benghazi neighborhood - in several stages, he said. First, a small group of gunmen arrived, then a crowd of civilians angry over the film. Later, heavily armed men with armored vehicles, some with rocket-propelled grenades, joined, swelling the numbers to more than 200. The gunmen fired into the air outside the consulate. Libyan security guarding the site pulled out because they were too few. "We thought there was no way for the protesters to storm the compound, which had fortified walls," he said. Sharif said Libyan security advised the Americans to evacuate at that point, but he says the advice was ignored. There was shooting in the air from inside the consulate compound, he said. At this point, he said, the crowd stormed the compound. The consulate was looted and burned, while plainclothes security men were sent to evacuate the personnel. Stevens, he said, is likely to have died of asphyxiation following a grenade explosion that started a fire, el-Sharif said. Ziad Abu Zeid, a Libyan doctor to whom Stevens' body was taken, told The Associated Press on Wednesday that the 52-year-old Stevens died of asphyxiation. US officials have said attackers broke into the main consulate building at around 10:15 pm and set the compound on fire. Amid the evacuation, Stevens became separated from others, and staffers and security that tried to find him were forced to flee by flames, smoke and gunfire. After an hour, according to US officials, US and Libyan officials drove the attackers from the consulate. The next attack came hours later. Around 30 American staffers along with Libyans had been evacuated to the safe house while a plane arrived from Tripoli with a joint US-Libyan security group that was to fly them back to the capital, Sharif said. He said the original plan was for a separate Libyan security unit to escort the evacuees to the airport. Instead, the joint unit went from the airport to the safe house, possibly because they were under the impression they were dealing with a hostage situation, he said. The militant attack coincided with the joint team's arrival at the safe house, he said. That the attackers knew the safe house's location suggests a "spy" inside the security forces tipped off the militants, he said. US officials have not confirmed the account. They have spoken of an attack on the consulate's annex that killed two Americans, but said their report on the incident was still preliminary. Demonstrators attacked the US embassies in Yemen and Egypt on Thursday in protests against the film, and American warships were moved closer to Libya. President Barack Obama has vowed to bring to justice those responsible for the Benghazi attack, which US officials said may have been planned in advance. Secretary of State Hillary Clinton said Washington had nothing to do with the video, which she called "disgusting and reprehensible." Meanwhile, ABC News reported that police were sent to the California home of the man they identified as the producer of the anti-Islam film, Nakoula Basseley Nakoula, who according to authorities is frightened for his life. Sheriff's deputies were sent to the Cerritos, California home of Nakoula, 55, Thursday to protect him and his family, a senior law enforcement official told ABC News. According to a sheriff, the police were at Nakoula's home overnight Thursday but have now left, as media reports identifying him as the man behind "Innocence of Muslims," and listing his address, have circulated. Nakoula told the Associated Press in an interview outside Los Angeles that he was manager for the company that produced "Innocence of Muslims." He denied he directed the film and said he knew the self-described filmmaker, identified only as "Sam Bacile." But the cell phone number that the AP contacted Tuesday to reach the filmmaker who identified himself as "Bacile" traced to the same Southern California address where the AP found Nakoula. A senior official said that they also had sent local law enforcement officers to the production company "Media for Christ" on Hamilton Road in Duarte, California to keep watch on the facility, which authorities said was affiliated with making the film that has been a trigger for anti-US violence and protest in several countries. Reuters, AP contributed to the report Follow Ynetnews on Facebook and Twitter Receive Ynetnews updates directly to your desktop