Toronto firefighters have extinguished a blaze on the fourth floor of a downtown apartment building.

The fire was reported shortly before 7 a.m. on Thursday at a building on Bleecker Street, in the area of Bloor and Parliament Streets. The apartment building is operated by Toronto Community Housing

Toronto Fire Capt. Mike Strapko said 12 fire trucks and 45 firefighters were called in to fight the two-alarm blaze.

When firefighters arrived, smoke was so thick on the building's fourth floor that there was no visibility in the hallway.

A woman was rescued from the hall way on the fourth floor, firefighters said, and taken to the third floor of the building for treatment.

The woman is the resident of the unit that caught fire, officials said.

Paramedics said three adults have to be taken to hospital, but all injuries are non-life-threatening.