Les Coteaux fire victims ID'd as Patrick Gagnon and Karine Desrochers-Gauthier

An early-morning fire that killed four family members, including two young children, on Tuesday in Les Coteaux, Que., may have been started by a forgotten cigarette.

The fire killed Karine Desrochers-Gauthier, 32, Patrick Gagnon, 37, and two of their three children.

A regional spokeswoman with Quebec's provincial police service said Wednesday morning that a smoking device — a cigarette, for example — is currently being looked at by investigators as a possible source of the fire.

The small and relatively contained fire started in the living room of the home of Desrochers-Gauthier and Gagnon, on the third floor of a small apartment building on Des Bouleaux Street.

Four of the five victims were found in their bedrooms by first responders; the fifth person was found in the bathroom.

Michel Pitre, the regional fire chief for Lac St-François, said it did not appear as though the home was equipped with a smoke detector.

Victims identified

"I had a great year! Thanks for having contributed," reads Desrochers-Gauthier's final Facebook post late on Monday night.

Four hours later, a fire that started in the living room killed her, her partner Gagnon and two of their three children.

Desrochers-Gauthier, Gagnon and their four-year-old daughter, Laurie, died before they could be transported to hospital.

Their two-year-old son, Felix, died later. Eight-year-old Mathis, the sole survivor, remains in critical condition at Ste-Justine, a Montreal children's hospital.

Neighbour Anne Pelletier's seven-year-old son is best friends with eight-year-old Mathis.

She said her son is praying hard for his friend.

"He's wondering where he'll go after, who will take care of him, if he'll be able to see him again. He even asked, 'Mom, will I have to take the plane to go and see Mathis?'" Pelletier said through tears.

A Facebook page has been set up in memory of the family members who died in the fire.