Canada — If arson is confirmed to be the cause of the Slave Lake wildfire, it would be Canada’s largest and costliest manmade fire – but only one of many fires that are intentionally set in Alberta’s forests and fields every year.
In the past decade, Sustainable Resource Development has investigated 16,356 wildfires, 120 of which were confirmed to be caused by arson. An additional 574 blazes are suspected to have been intentionally set by arsonists since April 2000.
Wildfire information officer Geoffrey Driscoll said, in many cases, investigators can’t prove “100 per cent” whether it was arson or negligence.
So far, officials are releasing few details about the investigation into the cause of the Slave Lake fire, known as “Fire 65,” but say investigators followed “a systematic and scientific approach” based on weather conditions, the characteristics of the fire itself, and area where it originated. Tom Fee, a private fire investigator and member of the California Conference of Arson Investigators, said the first step in a wildfire investigation is usually to pinpoint exactly where the fire started.
“What we look for is the origin and the cause,” he said. “And you can’t find out how until you know where.”
Investigators rely on witness and firefighter statements to find a general ignition area, then narrow it down based on burn patterns that show in what directions the fire moved, Fee said.
Once investigators identify a general point of origin, they divide the area into a grid and comb through each square to look for a heat source that may have caused a fire.
Investigators must consider sources such as fireworks, electrical wires or automotive equipment as potential causes. But even if investigators find a suspicious item – such as the remnants of a matchbook or a staple that held a matchbook together – it can still be incredibly difficult to prove someone intentionally started a fire.