The Grand Prix wildfire, which scorched nearly 60,000 acres between Lytle Creek and Claremont and destroyed 136 homes in October, has been ruled “accidental but human-initiated.”
Investigators found no evidence of arson and concluded that the fire’s cause was most likely an exhaust spark from a motorcycle or all-terrain vehicle, a dropped cigarette or a spark from a cigarette lighter, said Don Atkinson, chief of the San Bernardino County sheriff’s arson unit.
“We have nothing to indicate an arson,” Atkinson said. “We’ve eliminated as much as we can, and we’ve eliminated all of what we call the deliberate causes.”
Last fall’s string of Southern California wildfires scorched more than 738,000 acres, destroyed more than 3,600 homes, killed 25 people and cost $142 million to fight.
The region’s deadliest wildfire, the Cedar fire in San Diego County, burned 280,000 acres, destroyed more than 2,200 homes and killed 15 people. It allegedly was ignited by a lost hunter who set off a rescue flare.
Investigators say they have identified the 19-year-old man responsible for accidentally setting the Playground fire, which began the evening of Oct. 25 near Crestline and merged the next day with the Old fire, which had started in Old Waterman Canyon in San Bernardino and later destroyed hundreds of homes there and in Devore.
Atkinson said the man, whom authorities won’t name unless he is formally accused, drove his large, older vehicle off a trail and into a weed-filled area so he and at least two passengers could get a better view of the Old fire.
“When he drove that clunker into the weeds, the car’s catalytic converter or some other hot part underneath touched the weeds and started the car on fire, engulfing it in flames,” Atkinson said.
The Grand Prix fire was discovered the afternoon of Oct. 21 in a brushy, flat stretch of land known as Coyote Canyon, parallel to a new housing development in Fontana just west of Interstate 15. The blaze raged west across the foothills of the San Gabriel Mountains for the next week, closing freeways, forcing evacuations, threatening thousands of homes and destroying structures ranging from rustic cabins above Rancho Cucamonga to million-dollar estates in San Antonio Heights and Claremont.
Atkinson, a nine-year member of the arson unit, said the most promising clue in the Grand Prix fire came from someone who lives near the fire’s starting point and heard a motorcycle on a dirt path in a brushy area.
“That’s as close as we can get,” Atkinson said. “There is a motorcycle trail that crosses a road near where the fire started, and clear evidence of motorcycle and [all-terrain-vehicle] tires impacting the road. We cannot disprove that this didn’t start because of [something incendiary] from a motorcycle’s exhaust system.”
Fire officials originally suspected an arsonist in the Grand Prix fire.
Atkinson said that the case remains open, and that the details he seeks from the public are along the lines of someone saying “they saw so-and-so was riding his motorcycle in that area that day.” Atkinson said the person responsible probably would be cited only for trespassing or illegal off-road riding.
Federal prosecutors are still reviewing the case against the 19-year-old they say was responsible for the Playground fire, and are considering charges of leaving the scene of an accident and leaving a fire unattended, said Thom Mrozek, a U.S. attorney’s spokesman. The driver did try to alert the fire department about the blaze, he said.
“This is not an arson case,” Mrozek said.
Sgt. Bobby Dean, leading the investigation into the Old fire, which was determined to be arson, said a five-member homicide team in the San Bernardino County Sheriff’s Department has received more than 600 tips and assembled a database of leads in the search for a suspect.
A composite sketch of a male seen throwing incendiary devices from a van in Old Waterman Canyon was released soon after the fire began, and there is a $110,000 reward for anyone who can provide information leading to a conviction.
“Some cases need time to marinate,” Dean said. “Time, in homicide cases, is not an enemy. A lot of times, time is our friend. We just need the right events to occur to cause information to come our way.”
Authorities have determined that the 44,699-acre Otay fire, which burned grass, chaparral and Tecate cypress forest in San Diego County, was accidentally set.
They say it was caused by someone starting a warming or cooking fire, according to Roxanne Provaznik, a spokeswoman for the California Department of Forestry and Fire Protection.
Times staff writer Janet Wilson contributed to this report.