FORT WORTH -- Fire crews say popular gay nightclub Rainbow Lounge has been destroyed by an overnight fire.

When it was closing time at about 3 a.m., the owner and manager noticed smoke coming from the top of the building and called 911, according to the Fort Worth Fire Department.

Firefighters arrived to find a "working fire" and went inside. Crews soon noticed the roof sagging and pulled the crew out of the building.

The roof then collapsed.

No injuries have been reported.

The cause of the fire is under investigation, but arson investigators believe it to be accidental in nature.

The building was secured after the fire was put out, the department says, but crews stayed on the scene until about 7 a.m. putting out hot spots and making sure no one went near the unstable structure.

Back in 2009, the Rainbow Lounge made headlines when Fort Worth police and TABC agents raided the establishment, arresting several for public intoxication, injuring two patrons, and prompting allegations of police brutality.

Protests were held in the following days, making Rainbow Lounge the epicenter of gay rights at the time.

Because of the raid, Fort Worth PD created a special task force, made changes to department policy, and went through diversity training.

<p>Rainbow Lounge on fire (Rodger Fisher)</p>