Four homes caught fire on Byng Avenue, near Danforth Road and Pharmacy Avenue at about 6 a.m.
According to firefighters the fire started in one house, but quickly spread to the adjoining houses.
Some residents said they smelled gasoline fumes and found traces of gasoline at the scene.
Police later said they found two homes and a car "covered in gasoline."
The house that was destroyed was under construction. The amount of damage to the other homes is still being assessed.
The fire was put out shortly after 7 a.m.
There were no reports of injuries.
Police took a man, described as a person of interest, into custody as part of their investigation into the fire. He was later released.
No further details were released.