Flames that killed four Canadian soldiers and left 19 people in critical condition began with a smoldering grass fire that quickly grew in an Alberta base’s training area where personnel were carrying ?out exercises, officials said on Sunday.

Officials said 39 people had been hospitalized?as a result of the fire at ?Canadian Forces ?Base Wainwright, which Prime Minister Mark Carney described as one of the worst peacetime tragedies for ?Canada’s military on home soil.

Winds up to 96 km per hour fed the blaze which began around 4 p.m. on Saturday. But they were below 50 km per hour leading up to the fire, Maj. ?Gen. Wade Rutland told reporters at a news conference.