A 73-year-old woman died overnight in an apartment fire in Pierrefonds.

The fire broke out around 1:55 a.m. in a building on Riviera St., near Riverdale Blvd. and firefighters quickly searched the apartment complex to determine where the fire had started.

"They found in an apartment there was a woman, age of 73, that was unconscious," said Const. Jean-Pierre Brabant of the Montreal police department.

"Unfortunately she was pronounced dead on site and for those reasons the investigation was transferred to the arson squad of the Montreal police department."

About 100 people had to leave their homes while firefighters were dealing with the smoke and fire.

“Alarm just went off in the middle of the night - about 2 o'clock, I think- so we had to get out of the building with the kids,” said one tenant in the building.

“They were taken care of and there was a bus from the STM that was used for shelter," said Brabant. The evacuees were allowed to return inside after firefighters determined there was no danger.

As is the case with all deadly fires, the investigation has been transferred to the police department's arson squad.

That unit's first order of business will be to determine the exact cause of the fire in the apartment, which at this point is suspected to be a cigarette or similar item. 

It is not known if there was a smoke detector in the woman's apartment, but some residents said they have detectors in their units and the building's alarm is tested regularly.