Four Canadian service members were killed and dozens more seriously injured in a fire at Canadian Forces Base Wainwright in Alberta, Prime Minister Mark Carney said Sunday, calling it one of the country’s worst peacetime military tragedies on domestic soil. The fire broke out in a training area shortly after 4 p.m. Saturday, according to the Royal Canadian Mounted Police. Strong winds pushed flames beyond the base and into nearby rural areas. By late Saturday, the Municipal District of Wainwright said the fire was being held and that property and critical infrastructure were protected. Residents were not ordered to evacuate. Authorities said there was no indication the fire was terrorism-related, but its cause remained under investigation. The RCMP and Canadian Armed Forces were involved, and Defense Minister David McGuinty described the response and inquiry as active and delicate. He said he would travel to Edmonton for a briefing. The emergency quickly strained medical services. Several Alberta hospitals declared Code Orange, a designation for a surge of severely injured patients. Acute Care Alberta warned that ambulance resources in the Edmonton area were extremely limited and urged people to avoid the University of Alberta Hospital emergency department if possible. Patients were transported to hospitals across Edmonton after the Wainwright-area facilities were overwhelmed. The town of Wainwright, about 7,000 people, was not equipped for a mass-casualty event, Mayor Bruce Pugh said. Helicopters and planes helped move patients to other treatment centres. Carney said the families of those killed had been notified and that the situation was still developing. Flags on federal buildings were to be lowered to half-staff. The military said it would not release casualty figures until relatives had been informed. CFB Wainwright is a major training installation where Canadian soldiers prepare for combat operations. It houses the Canadian Manoeuvre Training Centre and the 3rd Canadian Division Training Centre. The fire also disrupted advance voting ahead of a Monday referendum on whether Alberta should begin a process that could lead to independence from Canada. Elections Alberta said polling locations in Lloydminster and Vermilion closed early Saturday and that ballots were transported securely. Alberta Premier Danielle Smith called the fire significant and tragic. Saskatchewan Premier Scott Moe said his province was sending assistance, while Conservative opposition leader Pierre Poilievre urged people to follow emergency instructions and keep roads clear for first responders.