Montreal, Canada - Canadian Prime Minister Mark Carney on Monday promised a "thorough and rapid" investigation into how a fast-moving fire killed four soldiers and injured dozens of others at a training base.

The cause of Saturday's fire, which spread during an exercise at the Wainwright base in the western province of Alberta, remains unknown.

"Driven by ferocious winds, the fire jumped nearly a kilometer in less than a minute to where soldiers were gathered," Carney told parliament in Ottawa after members observed a minute of silence.

"Fifty investigators are on the ground. We will ensure that they have all the resources they need to complete their work thoroughly and expeditiously."

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Four soldiers died in the blaze, and 39 others were injured – 19 of whom remain in critical condition.

"Several members of our armed forces are still fighting for their lives," Carney said Monday.

Major General Wade Rutland told reporters Sunday that the soldiers were caught off guard by the advancing flames during an outdoor exercise on the Alberta prairie.

He downplayed reports of exploding oil and gas infrastructure and ruled out any outside interference.

The Wainwright base is one of the largest bases operated by the Canadian Armed Forces, and it regularly hosts training exercises involving military personnel from NATO countries.