Scenes from the crudely made anti-Muslim video are explicit: Men dressed in head coverings and robes beat and slash a girl wearing a cross and burn the homes of “forsaken Christians” as Egyptian police do nothing.

Excerpts from the amateurish, California-made video — called “The Innocence of Muslims,” although it is not clear that a complete film exists — have set off days of violence in the Middle East, and provoked condemnation from U.S.-based members of Egypt’s Coptic Christian minority.

A top U.S. Coptic official said in a statement that the church “strongly rejects dragging” the community into controversy because of “an inflammatory movie.”

But some evidence has emerged that at least two Coptic activists, one on each coast of the United States, were involved in promoting and producing the film, which depicts Islam’s most revered figure, the prophet Muhammad, as a vulgar, violent womanizer swaggering in the desert with a gang of thugs.

A 14-minute compilation of excerpts has been posted since Monday on the Web site of Morris Sadek, an Egyptian-American Copt who lives in Northern Virginia. Local Coptic activists said Sadek, who didn’t respond to repeated requests for an interview, sent e-mails promoting the video to hundreds of people, including local followers and journalists in Egypt.

The activists said that Sadek had been interviewed by telephone on television and radio in Egypt this week in connection with the video and that he routinely e-mails newspaper editors and opinion makers in Egypt.

Federal officials said Thursday that they thought a man named Nakoula Basseley Nakoula, 55, of Cerritos, Calif., played a role in making the video, though they declined to confirm an Associated Press report that Nakoula, whom the AP described as a Copt, was the “key figure” behind it. Officials said the FBI expects to learn more about the video as part of a broader probe into the attacks in Libya.

For now, one official said, the video’s origins remain a “mystery.’’ There is no indication that Nakoula and Sadek know each other.

State Department spokeswoman Victoria Nuland said Thursday that the video excerpts had been available well before Egyptians began organizing demonstrations. The video “had actually been circulating at a relatively low level for some months out there in cyberspace and . . . only caught fire in the region on the day or just before the day that we began to see these various protests,” she said.

Nakoula told the AP that he managed logistics for a company that produced the film and did not direct it but said he knew the filmmaker, Sam Bacile. A man by that name had earlier told the AP via phone that he was the writer and director. The AP said on Thursday that Bacile is a false identity and that the cellphone number used to reach him traces to the home of Nakoula.

A Southern California insurance salesman and anti-Muslim activist named Steve Klein told Bloomberg News that he advised the filmmaker on finding actors. The video was originally titled “The Innocence of Bin Laden,” Klein said, which the filmmaker predicted would attract an audience of radical Islamists who would then become disillusioned about their faith after watching.

The investigation into the film’s origins offers a window into an increasing number of vocal critics of Islam, from fringe figures who denigrate the faith to activists who say they just want to end radicalism. Some work to promote state measures banning sharia and others focus on zoning laws to halt mosques.

“It’s growing hugely,” said Daniel Pipes, a writer who focuses on radical Islam. “Before Sept. 11, there were like two of us. . . . I think what it represents is a growing insurgent anger against Islam.”

FBI and Homeland Security officials Thursday urged local and state law enforcement officials to be on guard against any possible retaliation against “the filmmakers or promoters of the film,’’ in addition to Jews, Coptic Christians or Muslims.

Terry Jones, the Florida pastor who has drawn scrutiny and censure by organizing Koran burnings and other anti-Islamic events, brought attention to the video when he began promoting it in a run-up to marking the Sept. 11 attacks.

Jones said he spoke twice Thursday with the filmmaker, who he said is going by the name of Sam Bacile.

“He said all his friends have forsaken him and he has no friend left except us. He takes no calls except from us,” Jones said. “I understand. Unless people are close to you, you lose all your friends.”

Sadek posted the video, with Arabic subtitles, on the Web site of the National American Coptic Assembly, a group he heads that is based in Chantilly. Several Coptic activists said they did not believe Sadek had played a role in adding the subtitles.

“He just wants to keep insulting Islam. He does not represent Copts, and we have excluded him from all our activities,” said Magdi Khalil, a Virginia-based activist with the rights group Coptic Solidarity. Khalil said that he is on Sadek’s e-mail list and that Sadek sends “very hateful messages. I am totally against what he has done.”

Mohamed Elmenshawy, an Egyptian scholar and journalist at the Middle East Institute in Washington, said that he had seen Sadek occasionally at conferences and public events and that he had become “a kind of celebrity” in some sectors of the Egyptian media because of his provocative and extreme comments.

“A film like this gives the radicals in Egypt more publicity than they ever dreamed of, because it was made by radicals on the other side,” Elmenshawy said. “They are both a tiny minority, but they have very loud voices.” He criticized Sadek for promoting a film that could make things worse for his fellow Copts in Egypt, where it is being portrayed as “the work of Copts in America.”

An advocate for American Muslims said Sadek does not represent popular thinking. “There is a tiny minority of extremist Copts waging a rhetorical campaign against Muslims and Islam from America, posting and broadcasting vile, hate-filled messages that are condemned by mainstream Copts here and in Egypt,” said Ibrahim Hooper, director of the District office of the Council on American-Islamic Relations.

In 2010, Nakoula was convicted on federal bank fraud charges in California and ordered to pay more than $790,000 in restitution. He was also sentenced to 21 months in federal prison and ordered not to use computers or the Internet for five years without approval from his probation officer.

A group who says its members worked on the film’s crew contacted reporters this week to say the crew had been duped by the filmmakers about the film’s subject. The group says its members wish to remain anonymous because they are worried about protests.

Filming took place last year, one person told The Washington Post on Thursday, with 60 actors and more than 30 crew members.

When crew members received the script, this person said, “the Muhammad character did not even exist.” The cast and most crew members never saw the full script, which they were told was being changed during production.

“We have been blindsided by the final product. If we had known this was the producer’s intent, we never would have participated in any way,” the person said. “We are all angry, feel very manipulated and overall anxious. We do not stand behind the film in any way. . . . We are disgusted.”

Sari Horwitz, Karen DeYoung and Alice Crites contributed to this report.