Residents living on Marquette street in the Plateau were woken up by what sounded like an explosion early Thursday.
A 911 call was placed around 2:45 a.m. and Montreal Police (SPVM) arrived to find a multi-unit apartment building filled with smoke and flames. Firefighters were called in.
A woman in her 60s was found unconscious in one of the units. First responders raced to save her life, and she was taken to hospital in critical condition. She is now stable.
The SPVM says another woman was treated on-site for burns to her lower body and a police officer was treated for smoke inhalation.
The cause of the fire remains unknown. Firefighters handed the investigation over to the Montreal police arson squad.
A perimeter is set up around the building, Marquette Street is closed between Laurier and Saint-Gregoire. Police say to avoid the area.