Los Angeles ? FBI Director Robert Mueller on Monday defended the agency’s use of informants within U.S. mosques, despite complaints from Muslim organizations that worshippers and clerics are being targeted instead of possible terrorists.

Mueller’s comments came just days after a Michigan Muslim organization asked the Justice Department to investigate complaints that the FBI is asking the faithful to spy on Islamic leaders and worshippers. Similar alarm followed the disclosure earlier this year that the FBI planted a spy in Southern California mosques.

The Council of Islamic Organizations of Michigan sent a letter to U.S. Attorney General Eric Holder after mosques and other groups reported members of the community have been asked to monitor people coming to mosques and donations they make. The FBI’s Detroit office has denied the allegations.

In the California case, information about the informant who spied on the Islamic Center of Irvine came out at a February detention hearing for a brother-in-law of Osama bin Laden’s bodyguard, an Afghan native and naturalized U.S. citizen named Ahmadullah Niazi.