Three people managed to escape with their lives as a massive fire laid waste to three buildings in the historic Kensington market neighbourhood.

Two residents climbed out onto the roof of one of the affected structures, at Spadina and Baldwin, and managed to get down to the ground safely. A third person was rescued by firefighters before the building collapsed. That person suffered smoke inhalation but is expected to be fine.

As many as 120 firefighters were on the scene at one point to fight the three-alarm blaze. Officials admitted it was a fast-moving fire, and that by the time they arrived the third floor had already fallen in.

"The fire progressed to such a stage that the whole roof area became involved so we went from an offensive attack removing all the firefighters from the inside of the building and brought them outside," described Toronto Fire Platoon Chief Larry Fry.

"We set up three aerials and their main objective was to knock down the fire in that area. The fire advanced south but we've been able to put a hold on it and we stopped the fire on fourth unit south of the corner building. That building has also suffered some pretty heavy fire loss through the roof area."

There's no indication what started the flames but it's believed the fire started on the third floor of the corner building.

Inspectors are looking into whether the building is structurally sound and that area homes and businesses aren't affected.

Some of the buildings in the neighbourhood date back to the 1800s.