Alberta Premier Danielle Smith said on Sunday that 39 people were in the hospital after a fire at a Canadian military base killed four people. At least 19 were in critical condition.

The fire broke out at Canadian Forces Base Wainwright, one of Canada's busiest military training bases, at about 4 p.m. local time (2200 GMT) Saturday.

Maj. Gen. Wade Rutland, commander of the 1st Canadian Division, said the army responded to a "serious fire incident" during a training exercise conducted by the Third Battalion, Princess Patricia's Canadian Light Infantry.

A grass fire ignited in the training area during the exercise, Rutland said at a news conference Sunday, adding that the cause was under investigation.

"What I would say is there was multiple training activities happening throughout the training area at the time," he said, adding that "uncommonly strong winds caused the fire to spread rapidly and shift direction towards the range administrative area."

Canadian Prime Minister Mark Carney on Saturday called the incident one of the worst tragedies the army has suffered in peace time.

"It is with deep sadness that I can confirm, at this time, that four service members have lost their lives and that their loved ones have been notified," Carney said in the capital Ottawa, adding that "dozens of others have been seriously injured."

"We will care for the injured through every step of their recovery," Carney said.

"And we will stand by the women and men of our armed forces as they bear the weight of this loss, they will not carry it alone because in Canada we take care of one another."

Medical facilities around base 'overwhelmed'
A doctor at a hospital in the city of Edmonton, which is located some 180 kilometers (120 miles) northwest of the base, told national broadcaster CBC that people were being brought to hospitals across the city.

Dr. Warren Thirsk, an emergency department physician at the Royal Alexandra Hospital, said health-care facilities around the base itself had been "completely overwhelmed" by the number of people requiring medical aid.

"This number of patients would overwhelm the city of Edmonton," he said. "It is more patients than any of us want to count right now. It’s a disaster. It’s a one in every 15 to 25-year disaster."

What else do we know about the major fire in Alberta?
The Municipal District of Wainwright said the fire was spreading rapidly due to high winds.

"The fire south of Wainwright crossed the base fence earlier today and is being actively managed ... Emergency crews remain focused on protecting life safety, homes, and other structures," it said.

The incident occurred just days before people in Alberta, home to the world's fourth-largest proven oil reserves, will vote in the October 19 referendum on whether the province wants to begin the process of separating from the rest of Canada.