MARIETTA - Marietta investigators say a Monday night fire that damaged a mosque on Powder Springs Street was intentionally set.

Marietta Assistant Fire Chief Scott Tucker said a prayer service ended about a half hour before flames engulfed the building around 11:30 p.m. The fire damaged the prayer hall of the Islamic Center of Marietta, Masjid Al-Hedaya, but no one was injured, Tucker said. On Tuesday afternoon, investigators were interviewing people who were at the mosque Monday night before the fire started.

Tucker said there was evidence of forced entry into the mosque and that the fire had been set from the inside. State arson investigators also inspected the scene on Tuesday afternoon and found evidence of a substance used to ignite or accelerate the fire, although they could not confirm what the substance was.

"We will continue to talk to as many people necessary," Tucker said. "Our goal is to find out who set the fire and we believe that somebody who attends this mosque is going to have that information ... There are five prayer services per day here. There's a lot of people connected with this mosque and we're hoping to talk to everyone that has been here recently."

The Council on American-Islamic Relations has also called for the FBI to investigate a possible biased motive for the fire.

Ibrahim Hooper, a spokesman for CAIR, said the call for an FBI investigation came from the fact that there have been several recent incidents around the country of crime targeted at mosques.

"There's been too many incidents around the country - whether it's targeting mosques or vocal opposition to mosques," Hooper said. "Just on Sunday there was a hate protest outside a mosque in Florida ... It's a combination of all of these incidents and just our past experience, at least a biased motive should be investigated. Whether it's ever uncovered we just have to wait and see and trust to the ability of local, state and national law enforcement agencies."

Tucker said investigators are not yet considering the fire a hate crime.

"I have to say that I don't consider it a hate crime until we find out how it was started," he said. "We've had other fires at churches that really had nothing to do with how they worshipped or who they were. This could have been just another building."

Tucker said the fire did not cause much structural damage to the mosque, but that the prayer hall is unusable.

Attempts to reach mosque officials were unsuccessful on Tuesday. The mosque occupies a two-story building on 4.5 acres at 968 Powder Springs Street.

The Masjid Al-Hedaya Islamic Center of Marietta has had its fair share of issues with the city. In 2008, a municipal court judge ordered mosque officials to tear down a deck because of issues with the mosque's building permit. One of the mosque leaders at the time, Mohammad Raza, was sent to jail briefly for refusing to demolish the deck.

In 2009, the Marietta City Council denied a special land use permit for Back to the Bible Church at 601 Tower Road to sell its property to Masjid Al-Hedaya.