Flames were burning a balcony as firefighters arrived at a building on Wesley Street in Moncton early Monday morning.
Platoon Chief Brian Gaudet said it appears the fire started on the second floor and worked its way around the building and up to the roof.
Firefighters received the call for help around 3:10 a.m.
More than a dozen fire workers were on the scene for more than four hours as they put out the fire. The building suffered extensive damage and is now unlivable, Gaudet said.
Gaudet said there were at least two units in the building. The occupants escaped unharmed.
The cause of the fire is under investigation.