The fire broke out just after 6 p.m. at 2130 Montgomery Street, a two-storey residential building between Ontario and De Rouen streets.
Division fire chief Robert Dubé said it took about 70 firefighters to put out the flames.
Seven people were forced from their homes and taken in by the Red Cross.
Dubé said the building suffered upwards of $150,000 in damages and will have to be torn down.
Police are still investigating the cause of the fire.