The cause of a four-alarm fire that tore through the roof of a three-storey building housing seven families remained under investigation Friday morning, hours after the blaze sent one Montreal firefighter to hospital.

Fire department spokesperson Francis Fleury said the fire occurred at about 2:15 a.m. in a building on Place Joseph-Michaud in the city’s Rivière-des-Prairies district.

The fire required the deployment of 120 firefighters, one of whom was sent to hospital with minor injuries.