Fire forced ten people - and at least two infants - from their homes around noon Tuesday.
It broke out in a three-storey residential and commercial building at the corner of St-Denis and Rosemont.
When a crew of approximately 70 firefighters arrived, the blaze had spread from the second floor to the roof.
Firefighters say no one was injured but the four apartments and a printing business on the ground floor were heavily damaged.
An STM bus was brought in to house the newly-homeless tenants.
It took over two hours to get the fire under control.
The fire appears to have started accidentally, but caused upwards of $300,000 of damage, firefighters said.
