The request sought records that described FBI guidelines and policies for surveillance and investigation of Muslim religious organizations, as well as specific information about FBI inquiries targeting 11 groups or people.

The lawsuit filed on Sept. 18 states that all the plaintiffs — who include some of the most prominent Muslim leaders in California — have reason to believe they have been investigated by the FBI since January 2001.

"It sends a message that Muslim-Americans have been, and continue to be, cooperating with law enforcement, but they’re concerned there might be a disproportionate focus ... on their religious practices," said ACLU attorney Ranjana Natarajan.

One plaintiff, Shakeel Syed, said that his organization and others have spent three years building a relationship with the FBI but that the agency’s resistance to the request was troubling.

"I think it is in the best interests of the government to come clean and be transparent and forthright," said Syed, executive director of the Islamic Shura Council of Southern California. "This is a credibility issue."

The groups filed an initial FOIA request in May 2006, several months after federal law enforcement officials confirmed the existence of a classified radiation monitoring program used in surveillance at mosques, homes and businesses.

At its peak, the secret program tested the air around 120 sites a day for signs of radiation that could be linked to terrorism.

The FBI responded to the request first by saying it couldn’t identify any records that met the criteria requested. After an appeal, the agency turned over four pages that dealt with the Council of American-Islamic Relations and Hussam Ayloush, the council’s executive director for Southern California.

Those documents dealt with a suspected hate crime at a mosque that the council had reported to the FBI and a conversation Ayloush had with an FBI agent about cooperating with federal law enforcers, Natarajan said.

She said she believes there are many more records because each plaintiff has been interviewed by the FBI or stopped at airports for questioning.

Ayloush, who said he is questioned by federal agents every time he flies internationally, said he had hoped the FOIA request would help him determine why he is stopped.

"Either ... we’re being stopped because we’re Muslims — which is morally wrong — or that the government must have some erroneous info linked to me that I need to be able to clear," he said.

The government has 60 days to respond to the lawsuit.