Investigators from the Office of the Ontario Fire Marshal are on their way to Windsor to investigate the fire at a downtown apartment building.
The fire in the 800-block of Ouellette Ave. broke out just before 3am Friday and was out within half an hour.
Three residents and a firefighter suffered injuries. Two residents suffered smoke inhalation; a third has been downgraded to critical condition, and a firefighter suffered a cut hand.
There is no word yet how the fire started, and fire officials are waiting for the outcome of the investigation before releasing how much damage the fire caused.