The wildfire that raged through northern Alberta and forced the frantic evacuation of more than 90,000 people was probably caused by humans, the Royal Canadian Mounted Police said on Tuesday.



After more than six weeks of investigation, police have determined the fire did not start naturally. “Wildfire investigators for the province of Alberta have established that the fire was most likely the result of human activity, having ruled out lightning as a probable cause,” the RCMP said in a statement.

Investigators are now exploring whether the cause is linked to any sort of criminal offence. The fire was sparked on 1 May near a wilderness area popular with outdoor enthusiasts and police are asking anyone who was there in the days before the fire to come forward.

Potential causes linked to humans, said Travis Fairweather of Alberta Wildfire, include campfires left unattended, debris caught in recreational vehicles and downed power lines. “We’re not ruling out any possibilities.”

He said it was too early to speculate on the consequences that could emerge after the investigation. “Within the Forest Protection Act you can be held accountable for the cost of putting out a wildfire, which, with a wildfire of this magnitude, could be a very high cost,” he said. “But that’s not an avenue they go down unless they think it was some real negligence on that person’s part.”

Authorities are also investigating what he described as “incendiary” causes, ranging from playing with matches to setting off fireworks to arson. If evidence is found to suggest the fire was deliberately set, the RCMP could pursue charges.

The fire was first spotted by an airborne forestry crew about nine miles south-west of Fort McMurray, a town of some 90,000 people in the heart of Alberta’s oil sands.

Dry conditions, unseasonably hot weather and shifting winds quickly transformed the blaze from one that was largely in control to a “nasty, ugly” inferno, in the words of the local fire chief, sending it swelling from about 1,200 hectares in size to its current size of nearly 590,000 hectares.

As it grew, its flames breached Fort McMurray’s city limits, prompting the hurried evacuation of the burning city. Residents jumped in their cars – often with little more than the clothes on their backs – only to be trapped in gridlocked traffic as flames licked the highway.

“It was something out of a movie,” resident Erica Decker said after the evacuation. “It was absolutely apocalyptic, there were vehicles stranded everywhere, the sky was black and orange, there were so many people trapped.”

After some 45 days of firefighting, authorities in Alberta said this week that crews had finally managed to gain the upper hand against the fire and had managed to halt its spread. Depending on weather conditions, it could take another month or two before the wildfire is completely contained and extinguished.

Earlier this month, the thousands of residents displaced by the fire began re-entering the city, starting the sluggish process of rebuilding their lives amid the rubble. The blaze destroyed about 10% of the city’s homes.

Oil sands projects in the region have slowly began ramping up production again, after the fire forced more than 1m barrels a day of oil sands production offline at one point.