The California wildfire that claimed the lives of two firefighters, ravaged more than 250 square miles and destroyed more than 60 homes was started deliberately, the US Forest service said today.
The Los Angeles County Sheriff’s Department launched a homicide probe and in the hills above the city, a team of forest service investigators hunted for clues to one of the largest wildfires in Southern California history.
Today the blaze continued to chew through a forest normally enjoyed by Los Angeles residents escaping the sweltering city.
The US Forest Service said Thursday the wildfire had been caused by arson.
Jeff Tunnell, a wildfire investigator for the Bureau of Land Management, said even in charred terrain, investigators could detect important signs in the soot.
“Fire creates evidence as well as destroys it,” he said. “We can follow fire progression back to the point at which it started.”
Investigators will start at the place firefighters were first called, then interview witnesses and look for indicators on the ground to work backwards to the fire’s place of ignition.
“You just follow your burn patterns,” said Mr Tunnell, a veteran of 50 wildfires who is based in Ukiah in Northern California.
He said clues could come from burned trees and grasses, where the amount of burned foliage tells investigators the direction and speed a fire was moving.
Once they find the general origin of the fire, investigators set up a perimeter and search the area in a grid formation until they find the actual place of ignition.
“We look for something that is not supposed to be there,” said forest service spokesman Nathan Judy. “Something out of the ordinary – is there a cigarette there? A party spot, debris, kids out there with fireworks?”
At the point of origin, investigators are often able to find the remains of whatever started the fire: a charred match or cigarette butt, a piece of metal from a car, a piece of power cable. If no such object is found, investigators will often rule a fire to have been “hot set”, meaning it was started by a person holding a lighter to the brush.
In November 2007, a fire in Malibu destroyed more than 50 homes, 35 other structures and burned more than 4,900 acres. Weeks later, five men were arrested after investigators found pre-cut fire logs and discarded food wrappers by a cave where an illegal campfire had been started.
By checking cash register receipts at a local store, investigators found the people most likely to have bought the logs and food, and used debit card records to track them.
Most wildfires are caused by human activity of some sort. The only exceptions are those caused by lightning and volcanoes.
Three years ago, arson investigators probing the cause of a wildfire in the San Jacinto Mountains that killed five firefighters discovered evidence of different types of incendiary devices found at several fires.
They recovered everything from simple paper matches to a “layover” that consisted of matches balanced on a single cigarette to more elaborate devices made up of wooden matches grouped around a cigarette and secured with duct tape or a rubber band.
The evidence was enough to build a first-degree murder case against mechanic Raymond Oyler.
In March, the evidence was used to convict him and send him to death row.