"There were people hanging out windows when we showed up," said Bill Clark, the fire department's deputy chief of operations.
"We were very fortunate that a lot of people weren't lost in this fire."
Three adults and one child were taken to hospital in unstable condition, Clark said. More than a dozen others were also treated in hospital for less serious conditions, like smoke inhalation.
One firefighter who suffered minor injuries was treated and released from hospital.
The building, which Clark estimated was built near the turn of the last century, was completely destroyed.
Clark said there were flames in the basement and ground floor of the building when the first crews got to the scene. He said they managed to assist some people out of their suites through the smoke-and-flame-filled hallways and out the doors, but eight people had to be taken out through windows and down ladders.
He said the remaining firefighters were told it was too dangerous to stay inside, but they asked for 30 more seconds to wrap up their rescue operations. When they finally got out, Clark said the entire building was on fire.
"The whole building was engulfed. Then we worked to defend neighbouring buildings," Clark said.
"It was pretty spectacular."
There's no word yet on what caused the blaze.
Const. Jason Michalyshen said there have been accounts of possibly suspicious activity near the building before the fire, and that the arson strike force is investigating.
He said police have a number of people in custody who might be witnesses or suspects in the fire, but no charges have been laid.
Steve West with the City of Winnipeg said 18 people who lived in the building have lost their homes. About two dozen others who live in the buildings on either side of the one that burned have also been evacuated and may not be allowed to return for several days due to smoke and water damage.
The provincial government, as well as the Red Cross and the Salvation Army, are helping people who don't have anywhere to go find places to stay.
"The folks from the block that was on fire have lost everything," West said. "The building itself was a total loss. It has collapsed."
Damage is estimated in the neighbourhood of $600,000.