The main building of a Listowel sawmill has been destroyed by fire overnight.

Firefighters were called to Keeso Sawmill on Highway 23 Sunday about 10:30 p.m.

More than 100 firefighters were involved in fighting the blaze. Crews are expected to be on scene throughout the morning.

The Ontario Fire Marshal’s Office was called to investigate.

Damages could be as high as $1 million.