The fire broke out at a used car sales centre at 16 Ingram Dr., which is just east of Keele Street north of Eglinton Avenue West.
At about 2:20 a.m. 911 callers reported seeing a burning building. .
No one was hurt in the fire.
Fire officials told CBC News the businesses were still operating but neighbours say the used car sales business had moved out recently. The building, they say,was being used to store clothes.
Neighbours also said crews had been seen in recent weeks working on the roof.
At its height, a total of 15 fire vehicles and 65 firefighters were battling the fire.
The intersection of Keele Street and Ingram Drive was expected to be closed through the morning rush hour — and firefighters are expected to be on scene all day.
Toronto Fire platoon chief Trevor Trotter said when firefighters arrived they found an extra obstacle.
"There was a pit bull. As I said, crews were concentrating on the building to the east and the pit bull was in a fenced in area — actually the fence was open and he was loose, and quite angry."
The owner arrived a short time later and collected the animal. The dog was not injured.
The Ontario Fire Marshal’s office has been called in to investigate.