Arson investigators are looking into a report of a man seen near the location where two brush fires started Wednesday morning on both sides of the 57 Freeway in Diamond Bar.
The fires forced the shutdown of northbound lanes early Wednesday.
About 10 acres burned on the northbound side of the freeway about 30 miles east of downtown Los Angeles. Five acres of grass were scorched on the southbound of the road, where the fire burned uphill.
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The fire was contained by mid-morning.
Investigators said they received a witness report of a man seen near the fires at the Toner Canyon exit. The man, wearing a white scarf on his face, was driving a black sedan, accordingo to the sheriff's department.
More details were not immediately available. Authorities did not confirm whether the fires were deliberately set.
All drivers were diverted off the freeway early Wednesday at the Tonner Canyon exit. Some lanes reopened later Wednesday morning, but traffic was slow.
The fire was first reported at approximately 2:15 a.m., according to the California Highway Patrol. No structures were threatened.
Anyone with information for investigators was asked to call 323-881-7500.