Investigators are trying to determine the cause of a fire that broke out in downtown Barrie business.

Firefighters were called to Bradford Street at around 6 a.m. after flames and smoke were found on the second and third floors of the building.

The building is used both as a dentist's office and an apartment. No one was in the building at the time.

“Our crews entered. It took about a half hour to 45 minutes to bring everything under control,” says Barrie deputy fire chief Gord Beilby.

Damage is estimated at half a million dollars. Investigators believe the fire started on the third floor or in the attic, but they still don't know how.