Orillia Fire was called to Studabakers Beachside Bar and Grill around 3 a.m. Monday morning for a blaze.
Firefighters are still on scene at the restaurant located at 211 Mississaga Street East, according to a spokesperson for the department.
"Heavy damage inside. The cause is unknown at this time," said Fire Chief Ralph Dominelli.
The fire department is asking people to avoid the area. Orillia Fire tweeted that the blaze is under control.
