MONTREAL - A child playing with a lighter likely caused a fire that ravaged a triplex and killed four people, including a seven-year-old boy, Montreal police said Monday.

Arson investigators who combed through the debris of the devastating blaze could not find any criminal intent behind the fire, said Montreal police spokesman Const. Olivier Lapointe.

"It was accidental," Lapointe said. "We think that it might have been a kid who was playing with a lighter in a room and this is how the fire started."

Lapointe said the child may have lit up some clothes or drapes in the apartment where the people were killed. It was not clear if the child in question is the one who died.

The blaze started shortly before dawn on Sunday and sent residents of the triplex spilling into the street and neighbours rushing out to help them as fire trucks arrived.

A 37-year-old woman and a man in his 40s were pronounced dead at the scene, while a 40-year-old woman and the young boy died later in hospital.

A man and a child managed to escape unharmed.

Another 15 people were evacuated from the building's five other apartments. One woman was taken to the hospital to be treated for shock.

More than 100 firefighters fought the five-alarm blaze.