Three children and two adults died in a house fire in Brampton, Ont., on Monday as firefighters risked their lives to battle the flames, a fire chief said.

Brampton Fire Chief Bill Boyes said local fire crews were met with heavy smoke and flames when they arrived on the scene of the fire at Conestoga Drive and Sutter Avenue around 2 a.m.

"Our hearts are absolutely breaking," Boyes said.

"What happened here today, to lose three children and two adults, with one additional person in life-threatening condition, it's absolutely tragic."

Const. Heather Cannon of Peel Regional Police said two children were taken to a local hospital where they were pronounced dead, while a third child was pronounced dead at the scene.

Cannon said two adults were also pronounced dead at the scene. Two remaining adults were able to get out of the home and were not hurt, she added.

A third adult was sent to a local hospital, Cannon said, but has since been transported to a trauma centre where they are in critical condition.

Boyes said the ages of the children are believed to be six, eight and 11. He added that the two adults who died are believed to be their parents.

The fire department did everything they could to rescue the occupants of the home, the chief said.

"They risked their lives to go into this fire and get these people out," Boyes said, noting mental health resources would be made available to the firefighters.

"Unfortunately, it was a terrible outcome."

Boyes said firefighters were working to ensure there were no hotspots in the home on Monday morning before an investigation into the cause of the deadly fire could begin.

The investigation will be done in collaboration with the Office of the Fire Marshal, Peel Regional Police and Brampton fire investigators, he noted.

Premier Doug Ford expressed sadness at the "tragic deaths."

"I just can't imagine the hurt being felt by the family, the friends and the community. You'll all be in our prayers," he said during an unrelated announcement in Brampton on Monday

Prime Minister Justin Trudeau, who was with Ford, said his thoughts were with family and friends of those who died.

"We're all thinking of those affected by this horrible, heartbreaking tragic fire," he said.

Brampton's fire chief urged the public to follow fire safety procedures.

"If you're at home, check your smoke alarms. Make sure you have a working carbon monoxide alarm. And make sure your family and your friends and all those that you live with know what to do in the event of a fire, know how to get out," Boyes said.

"We just don't want to see in Brampton or across Ontario another tragic fire happen."