Investigators say the 245-acre Dog Rock fire at Yosemite National Park is believed to have been caused by sparks from a vehicle.
Yosemite National Park Fire Investigators and Cal Fire said the sparks could have come from trailer safety chains dragging on the pavement, vehicle brake parts or other sources.
The extremely dry conditions at the park would have made it easy for a single spark to start a wildfire, Yosemite National Park said in a statement. The Dog Rock fire was only 10% contained as of Thursday.
Park officials urged visitors to make sure their vehicles were well-maintained and operating safely.
A pilot fighting the blaze died Tuesday. Geoffrey Craig Hunt was flying one of four planes being used in the initial attack on the Dog Rock fire. The contract pilot with DynCorp International, which operates Cal Fire's fleet of air tankers, was flying a Fire S-2T fixed-wing tanker when he crashed.
The tanker crashed into a 2,500-foot granite cliff near El Portal, the park's west entrance.