York Regional Police say a fire broke out at the back of a home in Markham on Saturday morning.
Emergency crews were called to Forest Park Cresent, near Henderson Avenue and John Street, at around 8:30 a.m. Saturday for reports of a house fire.
Police said the fire spread to a neighbouring home causing significant damage as the roof may have collapsed.
Firefighters have the fire under control and are on scene putting out hot spots, police said.
No injuries were reported.
The cause of the fire is not yet known.