From Peterborough This Week,

A Stewart Street apartment fire last Thursday is now being investigated as an arson.

Officials with the Ontario Fire Marshal's office and the Peterborough Fire Department have determined the blaze was "incendiary," which means it's suspicious.

"It started in the stairwell of the building that leads to the five apartments at the back," says Steve Whitehill, fire prevention officer with the local fire department.

"We don't know how it started but we know it was in that area."

Evidence collected at the scene has been spent to Toronto for testing and the investigation has been turned over to city police.

The fire started late Thursday afternoon. Upon arrival, firefighters found heavy smoke coming from a rear apartment at 333 Stewart St. The first crew gained entry to a rear stairwell and fought their way up to the third floor, where the heaviest fire damage occurred. The fire was brought under control in about 20 minutes.

There were no injuries but damage is estimated at about $150,000.

The Peterborough County Disaster Trust Fund assisted 22 people displaced by the blaze, many of whom did not have fire insurance.