Fifty investigators are examining a fire at a Canadian military base that killed four soldiers and injured 39 others, Prime Minister Mark Carney said Monday.

Questions are mounting over why training continued even though officials knew a fire was burning nearby.

Carney told Parliament in Ottawa that the Canadian Forces National Investigation Service is leading the investigation.

The Royal Canadian Mounted Police is supporting it.

The fire happened Saturday at Canadian Forces Base Wainwright in Alberta.

Carney said a fire was burning in the training area when strong winds pushed it nearly a kilometer in less than a minute toward gathered soldiers.

He said investigators have not determined what ignited the grass fire.

He later told reporters that the government would get answers as quickly and transparently as necessary.

The fire overtook soldiers from the 3rd Battalion, Princess Patricia's Canadian Light Infantry, and Army reservists doing live-fire training.

Nineteen of the injured were in critical condition as of Monday.

Opposition leader Pierre Poilievre, who represents Wainwright in Parliament, said many suffered severe burns needing weeks or months of intensive care.

Maj. Gen. Wade Rutland said Sunday that officials knew about the fire for hours but believed it was contained, so training continued before winds suddenly shifted.

About 84 soldiers from Charlie Company were training at two locations, and the fire swept into the second area.

Carney said the soldiers were preparing for a mission next spring to reinforce Canadian troops with NATO in Latvia.

The military identified the dead as Sgt. Morgan Wong of Edmonton; Pvt. Shaun Farrell of Prince Albert, Saskatchewan; Pvt. Aidan Goulding of North Vancouver, British Columbia; and Pvt. Hayden Lykkemark of Langley, British Columbia.

Carney ordered flags lowered to half-staff on all federal buildings nationwide on Sunday.

Military liaison officers are assisting families at hospitals in Edmonton, Calgary, Red Deer and Wainwright.

Mental health teams and chaplains are supporting soldiers and their families.