Sarnia fire officials and the Ontario Fire Marshal's Office are investigating the cause of an apartment fire on Confederation St.
Firefighters responded to the 200-block just before 8pm on Wednesday, after callers reported heavy smoke coming from the ground floor unit of a four unit apartment.
All occupants were already safely out of the house when firefighters went in.
The fire department says crews were able to quickly knock down the blaze and prevent damage to other units.
An estimate of the damage is not yet available.