The Monday morning fire at a Maryland Street rooming house caused about $300,000 damage.
Winnipeg police said the cause has not been determined and it remains under investigation.
Several people in the three-storey home got out safely when the fire started just after 10 a.m.
The fire started in the sub-structure between the second and third floors.
Initial fire crews believed they had quickly put out the fire and were inside examining the structure when the fire started up again, forcing firefighters outside.
Flames were shooting through the roof. An aerial truck was used to pour water on the building and bring the fire under control.