The bodies of Zahra Abdille, 43, Faris Abdille, 13, and Zain Abdille, 8, were found in the building (at 85 Thorncliffe Park Drive) following an earlier incident on a nearby highway.
Cause of death has not been released.
Police say investigators are working with traffic services on a possible connection with the death of a man on the Don Valley Parkway on the same day.
The man fell to his death hours before police came upon the three dead bodies, closing the southbound lanes.
The homicide investigator handling the case said Sunday there is "some correlation" between the two incidents, but called it "very non-tangible at this time."