Ontario Provincial Police are investigating the cause of an overnight fire in downtown Fort Frances.

Members of the Fort Frances Fire Rescue Service were called to the back of a building in the 400 block of Portage Avenue just before 11 p.m. Tuesday.

Eleven firefighters responded with a pumper truck and rescue truck.

There were no injuries reported.

The damage was limited to the back of the building that was once a veterinary clinic.

A shed was also destroyed.

No cause has been immediately released.

The Ontario Fire Marshall’s office is also involved in the investigation.