Fire crews battled a five-alarm blaze at a highrise in North York Thursday evening that injured two residents and two firefighters.

Emergency crews were called to a Toronto Community Housing building on Bathurst Street, south of Steeles Avenue West, just before 8:30 p.m.

Toronto Fire said a female victim was found on a fifth-floor balcony. CPR was administered before the woman believed to be in her 70s was taken to a trauma centre in life-threatening condition.

"They were unable to actually get her down through the hallway because of the significant heat and smoke conditions," Acting Fire Chief Jim Jessop told reporters at the scene.

"We used an aerial ladder, and we carried her down and transported her to Toronto Paramedic Services, who provided excellent care and transported her to hospital."

A second person was also rescued from the fifth floor and was taken to hospital in serious condition, Jessop said.

Highrise fire

Two firefighters who suffered smoke inhalation were sent to local hospital, both in serious but non-life-threatening condition, Toronto paramedics said.

Jessop described the conditions on the fifth floor as significant, saying fire crews "took a beating."

"Close your eyes and think of the heat and the smoke coming out of a fire in a chimney. That's exactly what our staff had to fight their way through to knock the fire down and to commence their searches," he said.

As of 11 p.m., the fire has been brought under control, Jessop said, adding that they have also completed their primary and secondary searches.

"We're happy to report that there have been no further individuals located in the building," he said.

The fire escalated rapidly from a second alarm to a fifth alarm because the blaze was climbing up and extending to the sixth and seventh-floor units, Jessop said.

Approximately 50 firefighters were on the scene at the height of the blaze.

Jessop said the fifth floor sustained extensive damage.

North York fire

While most of the residents sheltered in place, he said some people evacuated the building. He noted that it is more dangerous for fire crews to empty the highrise, given the amount of smoke inside.

"We've communicated to them that if there's any issues of smoke, or any other issues to call 911, and we will send firefighters to their units," Jessop said.

"We will work with the Office of Emergency Management and Toronto Community Housing to make sure that everybody is taken care of tonight and has a place to live."

Toronto Fire investigators are on the scene to probe the origin and cause of the blaze. The Ontario Fire Marshal has also been notified.

"Our crews will be here all night and well into the morning. We have to make sure that there are no hotspots," Jessop said.

"We are doing air monitoring throughout the building to make sure the air is safe for those that are sheltering in place."