Calgary Trail was closed at 76th Avenue Friday night as crews responded to behind the Billingsgate Seafood Market in south Edmonton.
A police officer happened to be driving past the scene when he spotted the fire.
The district fire chief said that when crews arrived there was a shed fully engulfed in flames.
Firefighters found evidence that homeless people may have been living in the shed.
About 20 firefighters worked to put out the blaze before it could threaten other buildings in the nearby area.
One firefighter rolled his ankle fighting the blaze but there were no other injuries reported. There is no damage estimate at this time.