Crews were called to the first fire around 8:30 p.m. It was burning in a trash can outside a building on Simms Street, which it briefly threatened to engulf. (CTV)

Firefighters put out two separate trash fires in a Vancouver Island city Friday night, and members of the public put out a third, according to the local fire department.

Courtenay fire inspector Greg Lamb tells CTV News Vancouver Island via email that Mounties are investigating the string of blazes in trash cans and dumpsters in the city overnight.

Crews were called to the first fire around 8:30 p.m. It was burning in a trash can outside a building on Simms Street, which it briefly threatened to engulf.

"Momentarily it was upgraded to a structure fire since it was being spread into a building," said Courtenay Fire Department Capt. Jonathan Welsh at the scene.

The building suffered "exposure damage" and scorching to its stucco exterior, as well as to a roll-up metal door, but crews were able to get the fire under control before it spread further.

Welsh said fires in the area have the potential to spread quickly through the older buildings densely packed into the neighbourhood.

"(It's) definitely an older part of Courtenay," he said. "It's a high-risk area."

Welsh said the first fire of the night was suspicious and that fire inspectors were hoping neighbourhood residents might have video of what the fire looked like before crews arrived.

Lamb did not provide the locations of the other two fires put out overnight.