The Ontario Fire Marshal has been called in to investigate an early morning blaze at 943 Ottawa Street.
Emergency crews were called to the scene around 1:40 a.m. Saturday.
It took almost five hours to fully put out the fire, which started in the basement.
One firefighter was hospitalized for smoke inhalation and released shortly after.
Nobody else was hurt.
The building houses five apartments as well as Alibi's Family Grill restaurant on the main floor and a basement art studio.
There is no damage estimate at this time but it is expected to be in the area of hundreds of thousands of dollars.
