Investigators are working to determine the cause of a fire that badly damaged a brick building Wednesday night in downtown Coeur d’Alene.

The building at East Sherman Avenue and North Fourth Street houses the Beacon Pub and the national headquarters of Pita Pit, a fast food chain.

The building did not have fire sprinklers, which were not required, Coeur d’Alene fire inspector Craig Etherton said Thursday. The city’s building department deemed the structure unsafe to occupy for now.

The fire appeared to have started in a Pita Pit computer server room on the second floor, Etherton said.

The second and third floors sustained smoke and fire damage, and the first floor, which houses Beacon, was flooded in the firefighting effort, Etherton said. Inspectors haven’t determined a cause, but the fire doesn’t appear to be suspicious, he said.

The Coeur d’Alene Fire Department’s entire fleet, plus several vehicles from other departments, responded to the three-alarm fire about 7:15 p.m., and crews remained on scene until about 11:30 p.m., Etherton said.

“Fortunately, we got a good knock-down on it,” he said. “They were chasing smoke for hours and hours, making sure there weren’t small fires underneath something.”

To thank the firefighters, employees at the Pita Pit restaurant across the street churned out more than 40 flatbread sandwiches, said manager Lauren Casey. They also provided drinking water for the firefighters.

Casey said the damage was minor enough that employees still were allowed inside. “It just smells like smoke,” she said.

Meanwhile, the cause of another recent commercial fire in Coeur d’Alene also remains undetermined. That fire gutted a strip mall Aug. 4 at North Fourth Street and East Hazel Avenue, and the building remains boarded up. Etherton said inspectors have a working theory to explain the blaze, and a determination is expected within a week.