Toronto Fire Services responded just after 8:30 a.m. to the fire at 198 Fairbank Ave., near Castlefield Avenue, just north of Dufferin Street and Eglinton Avenue. The fire was originally listed as a two-alarm fire and upgraded to three alarms shortly before 10 a.m., then four alarms by 10:40.
By 10 a.m., the fire had broken through the roof and Toronto Fire Services were asking people to avoid the area due to heavy smoke.
A spokesman told CBC News it looks as though the fire started in the office of the large factory.
A total of 12 trucks and 45 firefighters are responding.