OPP, paramedics, and crews from several stations were called out to a structure fire just east of Stratford on Sunday afternoon.
Provincial Constable Barry Cookson says approximately 40 firefighters were called to the former Stratford Antique Warehouse on Forest Road in Perth East.
There was no one inside the building at the time, and no one was injured.
There's still no damage estimate available, and the Ontario Fire Marshal's Office has been contacted for the investigation.
Due to the extent of the operations, Highway 7/8 had to be temporarily shut down at Perth Road 110.
The highway fully reopened late Sunday evening.