MONTREAL -- An unattended cigarette may be behind a fire inside an apartment in Lachine late Friday that left a woman and her eight-year-old daughter dead and her five-year-old daughter fighting for her life, police said Saturday.

Five members of one family were inside the apartment when the fire broke out around 11 p.m. Friday, Montreal police said, in a 51-unit building in Lachine in the city's west end.

The mother, 40, and her eight-year-old daughter were pronounced dead in hospital while her four-year-old daughter remained in critical condition in hospital on Saturday.

Const. Jean-Pierre Brabant said during the fire, 13-year-old twin brothers jumped from a second-storey balcony to evade the flames, suffering minor injuries.

The teens were taken to hospital and investigators hope to meet with them later to find out what transpired inside the unit. Neighbour Alain Makelele said he and another man caught the boys after they jumped.

"They were crying that their mother was still in there with their little sister and as soon as we were in sight of it, the apartment was in flames," he said. 

Montreal police arson investigators took over the probe Saturday because of the deaths.

Brabant says investigators are working with a hypothesis that a forgotten cigarette sparked the fire.

"There's still analysis that has to be done by investigators to confirm all that," Brabant said. "The first hypothesis we are looking at is a cigarette that was forgotten that caused the fire."

A small collection of stuffed animals sat at the front door of the building on Duff Court Street and hand-drawn pictures were taped to the glass after investigators opened up a large perimeter.

No one else was injured in the fire.

The Montreal fire department said they came face to face with an intense blaze when they arrived at the scene.

Operations chief Matthew Griffith said when firefighters arrived, the blaze was intense enough that 70 firefighters were called to combat it.

"There was a smoke alarm in the apartment," Griffith said. "Was it functional or not, it's difficult to determine for now because of the intensity of the flames and the heat at the arrival of firefighters."

This report by The Canadian Press was first published on Nov. 9, 2019.