Montreal police are investigating a fatal fire in the city's Villeray district.

The major fire started just after 10 a.m. on Monday and tore through a triplex on Christophe-Colomb Ave. between Villeray and Everett streets.

As many as 125 firefighters battled the fire.

On Tuesday, officials said they were concerned about a missing man who may have been killed inside, but fire crews were forced to wait until the building was safe enough to search.

Montreal police spokesman Manuel Couture said the fire is considered suspicious and investigators have a difficult task ahead.

"They have to identify the body first to know exactly who was there and after they have to determine exactly what caused the fire," Couture said. 

Officials have not confirmed whether accelerants were found on the scene.

Villeray fire

Firefighters tear down building that was destroyed by fire this morning in search of a body they believe to be inside. (Jessica Rubinger/CBC)

Residents interviewed at the scene reported hearing an explosion around the time the fire began and firefighters suspect the incident may be gas-related.

Another 43-year-old resident of the building suffered minor injuries in the fire.