Canadian military police are continuing to investigate a wildfire that killed four and injured 39 on the Canadian Forces Base in Wainwright, while a Board of Inquiry will later conduct a separate independent look into the incident.

Canadian Forces Provost Marshal Brig. Gen. Vanessa Hanrahan on Thursday confirmed the fire began inside an Automatic Grenade Launcher range and started during routine military training activities. The fire was inside a “permanent danger area,” which Hanrahan said restricted firefighters’ ability to suppress the fire and forced them to only observe it.

The fire’s “rapid” spread, characterized by Maj. Gen. Wade Rutland in officials’ first press conference on the tragedy, was caused by a “change in wind direction and velocity,” and wasn’t worsened by the base’s methane gas infrastructure, according to Hanrahan.

“Investigations of this nature are complex and require careful assessment of information and evidence from multiple sources,” Hanrahan said. “While there is significant interest in understanding what occurred, it is important that the investigative process be allowed to follow the evidence wherever it leads.”

Hanrahan said the Military Police were conducting an independent investigation to establish the facts and determine whether any criminal or service offence occurred. Comprehensive terms of reference are being developed for the Board of Inquiry to be formally convened.

The Canadian government previously confirmed the identities of those killed as:

• Sergeant Morgan Wong, from the Loyal Edmonton Regiment based at Edmonton, Alberta, serving with 3rd Battalion, Princess Patricia’s Canadian Light Infantry
• Private Shaun Farrell, from 3rd Battalion, Princess Patricia’s Canadian Light Infantry, based at Edmonton, Alberta
• Private Aidan Goulding, from 3rd Battalion, Princess Patricia’s Canadian Light Infantry, based at Edmonton, Alberta
• Private Hayden Lykkemark, from 3rd Battalion, Princess Patricia’s Canadian Light Infantry, based at Edmonton, Alberta

Officials previously said 19 of the military members who were injured were in critical condition, eight were stable, and 12 were receiving treatment for less serious injuries. Hanrahan did not share an update on the health status of those injured.