What ignited many of California’s worst wildfires a mystery

Cinfernos, more homes are being built in rugged areas where fire danger is high.

Three times as much acreage has burned so far this year in California as last year, which produced the Tubbs Fire that was the most destructive in recorded state history and the Thomas Fire that, until this year, was the largest ever.

And the most dangerous months for California wildfires are still to come.

The Carr Fire, the deadliest so far this year with eight fatalities, started in July with a spark from a vehicle. Whipped by winds, the flames exploded into Redding, the largest city in far Northern California. More than 1,000 homes were destroyed.

The driver immediately reported the fire so there was no mystery about how it started. Such quick confirmation is unusual.

“Trying to investigate any kind of fire is almost like trying to investigate a murder — except most of your evidence has been destroyed, and everything around it has been destroyed, by fire,” said Lynne Tolmachoff, spokeswoman for the California Department of Forestry and Fire Protection.

If lightning maps show no activity in a burn area, the assumption is it was started by humans, and fire investigators immediately head to the spot to cordon it off and protect evidence.

It’s a painstaking process, even when fires are small.

Investigators look at how the vegetation is flattened to determine where the flames originated and track it to the ignition point — usually the coldest spot.

But there are challenges, especially if the fire occurred along a road or other heavily trafficked area. Crews fighting fires can inadvertently wipe out key clues, like carbon particles from a car backfiring or pieces of porcelain from an exploded catalytic converter.

Cellphone photos and videos from witnesses help investigators. Drones provide aerial views of a point of ignition, showing burn patterns and strike marks on power lines, which are hard to see from the ground.

But often it comes down to two possible causes, which results in the cause being declared undetermined and the case being closed unless new evidence appears. Tolmachoff can’t recall an investigation to determine a cause ever reopening.

Last year’s Tubbs and Thomas fires still are under investigation.

Tubbs, in wine country north of San Francisco, destroyed nearly 5,700 structures and killed 22 people. Thomas, in Ventura and Santa Barbara counties, killed two people and destroyed more than 1,000 buildings. A month later, heavy rains fell on hills denuded by the fire, unleashing mudslides that killed 21 and left two others missing.

Lawsuits seeking billions in damages have been filed. Concern that California’s largest utility, Pacific Gas & Electric Co., would go bankrupt if it’s found at fault for the Tubbs Fire prompted the Legislature to pass a bill allowing the company to raise utility bills to pay off lawsuits.

alifornia officials quickly determined an ar sonist started last month’s huge wildfire southeast of Los Angeles, and that two weeks earlier sparks from a vehicle produced a deadly wildfire in the far northern part of the state.