Toronto Fire Division Commander Bob O'Hallarn told CBC News that five people were inside the Cedar Brae Boulevard home when the trouble started.
"Their lights flickered and then they heard a bang, and shortly after started noticing smoke," he said Sunday.
Smoke alarms went off, the family left the house and firefighters were soon called to the scene.
Sixty firefighters attended the scene, which O'Hallarn said was necessary because of the extent of the fire and the fact that the roof was collapsing.
The firefighters subsequently managed to subdue the blaze, though O'Hallarn said there was "very extensive damage" to the home.
No one was injured, which O'Hallarn said was a testament to the fact that working smoke alarms were installed.
There is no immediate estimate available on the damage caused by the blaze.