Damage from a hot-burning fire at Famous Dave’s barbecue restaurant in Kalispell Saturday night caused an estimated $250,000 in damage.

Kalispell police and fire officials still were investigating the cause of the fire Sunday night, but they say it started in the ceiling over the mechanical room.

From that point in the southwest corner of the building, it spread throughout the space between the Sheetrock of the ceiling and the membrane roof built with Styrofoam and tar, Kalispell Fire Chief Dan Diehl said.

The restaurant on U.S. 93 North still was serving dinner when the fire began, but all customers and employees were evacuated safely after an employee noticed smoke coming from the mechanical room.

The fire was reported to the 911 emergency dispatch at 9:41 p.m. Saturday. Kalispell firefighters were helped by fire crews from Evergreen and Whitefish.

Diehl said when they arrived, 20-foot flames were shooting through the roof at the southwest corner.

As two Kalispell firefighters prepared to enter the building, Diehl said an explosion from inside the building blew open doors on the north side and blew off the two firefighters’ helmets. They were not hurt, Diehl said, nor were any other firefighters injured during the long battle to locate and put out the fire.

He said they did not clear the fire scene until after 3 a.m. Sunday, although firefighters had the blaze contained shortly after midnight.

“We think at this time it was due to a buildup of natural gas in the kitchen area,” Diehl said. “It found an ignition source, but we don’t know what that was.”

On Friday, Kalispell Fire Department had been dispatched to the Famous Dave’s mechanical room when an electric motor was found burning.

Diehl said workers were in and out of the building all day Saturday trying to fix the damaged machinery.

A Famous Dave’s kitchen employee told the Daily Inter Lake on Saturday night the restaurant was having trouble with a water heater. The employee believed the fire began in the flue attached to the heater. He said kitchen staff tried to put out the fire themselves using an extinguisher before firefighters arrived.

The mechanical room is separated from the kitchen in the northwest corner by an office space in the middle.

Diehl said on Sunday that the natural gas apparently collected between the suspended ceiling and the membrane roof. The explosion blew smoke toward the dining area to the east end of the building but, he said, no fireball went with it.

All the fire was contained in the southwest corner of the building.

“The fire was contained in the space above the Sheetrock,” Diehl said. “They had to try to remove as much of the Sheetrock from down below as possible. We had a tremendous fire in that corner — it was not allowed to spread so it was extremely hot.”

He said the firefighters used thermal imaging cameras to locate where the fire actually was burning in the roof and wall. Heavy smoke inside the building and flames shooting through the roof made it difficult to see those images.

Firefighters from all three departments were chasing the fire in the roof and the west wall for quite some time, he said.

“We were trying to contain it there to reduce damage to the rest of the building,” he said.

Although fire damage was contained to the west end of the building, there was heavy water damage and smoke damage throughout.

“We had a pretty steady wind out of the southwest, which was pushing smoke into the rest of the building, and that contributed to the smoke damage,” Diehl said.

“The guys worked hard, it was difficult. A fire in a concealed space like that is time consuming. It takes a lot of equipment, a lot of saws,” he said.

On Sunday, a large hole cut through the west wall just above the roof line revealed charred timbers toward the interior. Cars pulled up to the parking lot in steady succession, filled with people curious about the situation.

Yellow police tape blocked all entries. Management had taped neatly printed signs to the entry doors, informing guests that the restaurant was closed due to a fire and apologizing for the inconvenience.

“Stay tuned for information regarding our reopening,” the signs closed. “Thank you for your patronage and we hope to see you soon here at Famous Dave’s.”