Twelve-year-old twins who were unconscious when firefighters carried them out of a burning townhouse unit in Gatineau, Que., died in hospital Sunday evening, the mother of the boy and girl told Radio-Canada.

Gabrielle and Jacob Rondeau twins Gatineau fire

Gabrielle and Jacob Rondeau, both 12, were asleep in their Gatineau, Que., townhome unit when a fire broke out late Saturday night. They died Sunday night in hospital.

Gabrielle and Jacob Rondeau were asleep on Saturday night when their 17-year-old brother left them alone in the townhome on Marengere Road to go get pizza with his girlfriend, he told Radio-Canada. 

Daniel Rondeau said firefighters were battling smoke and flames when he returned around 11 p.m. ET.

The twins were unconscious when they were rescued from their second-floor unit.

Neighbour Andre Valliquette said the twins had been at his home with his kids earlier in the night. A few hours after they went back to their townhouse, he said he heard the smoke alarm and rushed over to find a small fire on the kitchen stove.

Gatineau fire twins dead Gabrielle Jacob Rondeau

Teddy bears and flowers sit on the stoop of the townhouse on Marengere Road in Gatineau where the Rondeaus live. (Radio-Canada)

"It just blew into a big ball of fire, it just lit up so fast" he said. "I opened the door, but it was too late."

Gatineau police said Monday it was an accidental cooking fire and they're trying to determine if a pot of cooking oil was left on one of the stove's heating elements.

"We want people to make sure that when they are doing a cooking [oil] fire, they have to stay in front of the stove and make sure they … can extinguish the fire," said Eric Lajeunesse, of the Gatineau fire department.

No charges will be laid, police said.

More than 20 people were forced out of the four-unit building during the fire.