YOSEMITE NATIONAL PARK (CBS SF) — Yosemite National Park officials say sparks from a vehicle caused the wildfire in Placer County that led to a former U.S. Navy pilot’s death.

Fire investigators believe they have narrowed down the cause of the Dog Rock Fire near Applegate to sparks generated by hot metal fragments from a vehicle.

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They say it could be the result of several things such as trailer safety chains dragging on the pavement, vehicle brake parts generating a spark or other sources.

Geoffrey “Craig” Hunt, 62, of San Jose was flying a Cal Fire S-2T air tanker while fighting a fire in Yosemite National Park when the plane he was using to drop fire retardant crashed Tuesday afternoon.

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The fire has consumed 250 acres since it first started on Tuesday afternoon and has lead to a number of evacuations and road closures that lead to the park.

Five homes have been destroyed in the fires that began as a series of small fires along Interstate 80 about 40 miles northeast of Sacramento.

By Thursday the fire had burned through 420 acres, the California Department of Forestry and Fire Protection said. It is about 20 percent contained.

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The FAA and the NTSB were investigating the crash.