Investigators have determined the massive blaze in the central Alberta town of Penhold was not suspicious.
Last week, the fire destroyed an 18-unit apartment complex and sent two people to hospital.
Penhold Fire Chief Jim Pendergast says the source of the fire was likely a barbecue on a second-storey balcony.
About 50 firefighters from nearby Red Deer and Innisfail helped Penhold's volunteer firefighters to fight the fire, which took two days to completely put out.
Pendergast says the fire was the single most major blaze in Penhold in at least the last 30 years.