An explosion and fire at Canadian Forces Base Wainwright in east-central Alberta on Saturday killed four service members, Prime Minister Mark Carney said on Sunday, CBC News, Global News and CTV News reported. Their families have been notified, and dozens more are seriously wounded, Carney said at about 12:30 p.m. ET Sunday. He called it "one of the worst tragedies for the Forces on Canadian soil in peacetime," according to remarks posted by his office.

Separate military sources cited by Global News said at least seven people died. Sources cited by CBC News said seven people died. In a release late Saturday, the Department of National Defence said it would not confirm casualty details until families were notified.

Defence Minister David McGuinty said Saturday night that there had been "both fatalities and injuries as a result of an incident on the base," CBC reported. "I cannot recall an incident like this in recent memory," McGuinty said, according to CBC, Global News and CTV. He said the RCMP is involved in investigating, CBC reported.

A preliminary investigation suggests a munition from a live-fire training exercise sparked a fast-moving grass fire, which caused an explosion, Global News reported, citing military sources. The Department of National Defence said the fire started in the base's training area around 4 p.m. local time, CTV reported. Alberta's energy regulator said it had no reports of incidents involving oil and gas sites on the base, CBC reported.

Wind gusts of up to 100 km/h (about 62 mph) fed the fire, Global News and CTV reported. The Municipal District of Wainwright said the fire crossed the base fence, according to CBC, Global News and CTV. Around midnight, the municipality said the fire was being held, Global News reported.

Several Alberta hospitals declared a Code Orange, which signals a mass-casualty response, Global News and CTV reported. Those alerts ended on Sunday afternoon, and patients were moved to hospitals in Edmonton, Red Deer and Calgary, CBC reported. The base is about 200 kilometres (124 miles) from Edmonton, Global News and CTV reported.

Carney ordered flags on federal buildings lowered to half-mast, according to his remarks. Chief of the Defence Staff Jennie Carignan said, "Our priority remains the welfare of our members, their families and their community," Global News reported. Officials, including McGuinty, were due to give a briefing in Alberta on Sunday afternoon, CBC reported.

What we know: Carney said four service members died and dozens more were seriously wounded after an explosion and fire at CFB Wainwright on Saturday.
What we don't: Whether the death toll will rise, how many people were hurt and what set off the fire.