The Sonora Fire Department responded to a late-night kitchen fire that erupted at the Be Wok & Sushi restaurant in the Sonora Plaza Shopping Center on Mono Way Wednesday night.

Sonora Fire Department Chief Aimee New said when the first fire engine responded to the scene just after 11:30 p.m., smoke was drifting out over the parking lot onto Mono Way.

“They knew instantly they had a working fire that would produce that much smoke,” she said.

When firefighters reached the scene, they observed smoke, but not flames, drifting out from the rooftop, she said. As some secured a water supply, firefighters were unable to pry the door open and were forced to shatter the front door windows to make entrance to the building.

When they went inside, smoke was shoulder high in the dining area, but no flames were visible.

Following a hoseline to the back kitchen, firefighters passed through the double doors and were confronted with a thick bank of smoke filling the room, she said.

Units on the roof cut two ventilation holes about 3-by-6 feet long to provide visibility and alleviate the heat exposure for the firefighters.

A small glow appeared in the back of the kitchen, and in less than 10 minutes, the fire was extinguished.

The cause of the fire remains under investigation, but the department ruled out the possibility of an electrical fire.

When investigators pulled out the electrical outlets in the kitchen, there did not appear to be any indication that a spark or short had ignited a flame, New said.

The origin of the fire was in a storage racking area in the back of the kitchen near a freezer, she said, and investigators believed the restaurant was vacant at the time of the fire.

The stove area had been ruled out as a cause or origin of the fire, she said, and the commercial stove extinguishing system over the stoves did not activate during the fire.

Be Wok does not have a fire alarm or sprinkler system in the kitchen, she said.

Sgt. Chris Rogers with the Sonora Police Department would be the lead investigator for the fire, she said, and added that no members of the public or firefighters were injured.

Tuolumne County Fire and Cal Fire assisted with the firefighting effort, she said.

According to Tuolumne County Sheriff’s logs, the fire was reported at at 11:34 p.m. when a caller saw “smoke and flames” coming out of the restaurant.

The commercial structure fire was first called in by two passersby seeing smoke from the rooftop, New said.

Be Wok & Sushi owner Bonnie You said the business will be closed until a cause was determined and an insurance investigator evaluates the damage.

A large portion of the kitchen was burned and damaged by smoke, she said, but the fire had not spread to the dining area.

You said she and Be Wok employees were not there when the fire occurred, but she arrived Wednesday night after emergency personnel.

“We appreciate the customers, but I hope they have patience so we can open as soon as possible,” she said.

Contact Giuseppe Ricapito at (209) 588-4526 or . Follow him on Twitter @gsepinsonora.