Commercial building fire under investigation in Parksville, B.C.

Investigators are sifting through the damage after a fire at a commercial building in Parksville, B.C.

Firefighters were dispatched to the structure on Memorial Avenue at 6:03 a.m. Thursday.

On arrival, fire crews found flames in the back of the building on the second floor, according to Parksville fire Chief Marc Norris.

Firefighters believe no one was inside the building, which houses several offices, at the time.

"We had a structural collapse at the rear roof of the building, at which time we withdrew fire crews from the building and worked it from the exterior," Norris said Thursday.

"Because of the roof collapse there'll be pockets of fire burning under those areas so it will be a few hours of mopping up," the fire chief said.

Kevin Johnson told CTV News he was the person who called 911 to report the fire.

"I was just out for a walk in the morning, and just noticed smoke going down into the park," he said. "It didn't look right, so I just thought I'd check it out."

Johnson said he encountered "smoldering flames against the building at the top of the stairs," adding that the fire grew quickly in the wood-framed building.

Fire investigators have begun to comb through the damage to assess what caused the blaze.

"We've already started some basic investigation," Norris said.

"The RCMP are talking to people in the area and collecting video of the area to see if we can ascertain what the cause of the fire was," he added. "We're not sure if the fire started on the inside or the outside."