A rare, six-alarm fire at a downtown Toronto highrise building resulted in 14 people being sent to hospital and left an estimated 1,200 people temporarily homeless.

Eight adult civilians, three firefighters and three children required medical care, Toronto Fire Chief Bill Stewart told reporters late Friday.

Three of the eight adults suffered "very serious" cases of smoke inhalation, said Toronto EMS Chief Bruce Farr, with one requiring treatment in a hyperbaric chamber.

Stewart said one firefighter suffered a concussion, another was burned and a third suffered smoke inhalation. At least 10 had to be treated for heat exhaustion.

Compared to the situation an hour earlier, "We're winning the war on this one," Stewart said shortly before 11 p.m. However, firefighters would be working at the building long into the night, he said.

Stewart also said he had to order a complete evacuation of the building because he "can't guarantee the integrity of the structure."

The fire at 200 Wellesley St. E., near Bleecker Street, first broke out at about 5 p.m. on the 24th floor. It grew into a rare six-alarm fire, with more than 120 firefighters and 27 pieces of equipment at the scene during its peak.

At 8:30 p.m., when it seemed progress has been made, bright orange flames could be seen in the bedroom of one unit on the 23rd floor. By 10 p.m., firefighters appeared to have knocked the flames mostly down.

Stewart said "extreme fuel loading" in one apartment made the fire very difficult to fight. They rotated crews in from all over the city, he said.

The firefighters say this has been one of the "hottest," most deep-seated fires they have ever fought, he said.

The high winds Friday evening made matters worse, Stewart said.

Saaed Kamal lived on the seventh floor. He said he could smell smoke as he left the building through the stairwell. "I could not breathe very well as I went down the stairs," he said.

Resident and tenant representative Clifford Martin said the building is owned by the Toronto Community Housing Corp.

There are more than 700 units in the building. Many of the people are immigrants, and some have physical or mental health issues.

Dozens of residents gathered outside the Wellesley Community Centre watching the battle to extinguish the blaze. After night fell, they could see the firefighter's flashlight beams coming out of the apartments, appearing blue in the smoke.

One man said that he thinks the fire started in his unit.

Stephen Vassilev said he lived in the apartment with his cat Fonzie. He had been out helping a friend find a place to live when he arrived back at about 7:15 p.m. to find firefighters battling the blaze.

By looking on the outside of the building and doing some counting, Vassilev said he determined the fire broke out in his unit, which was packed with papers and documents.

"I have nowhere to go," he said, adding he might sleep in his car Friday night.

Toronto Community Housing was to use the community centre's gym for makeshift accommodations. The Canadian Red Cross is also trying to assist people.

It's not clear when anyone will be able to return.

The Ontario Fire Marshal's Office will be conducting an investigation to determine the fire's cause.

With a report from CTV Toronto's Sneha Kulkarni