That brings the total to $150,000, the Los Angeles Times reported. The state had already offered $100,000.
Two firefighters were killed when their truck went over a cliff, and dozens of buildings have been destroyed since the fire began Aug. 26. The fire has burned an area larger than the city of Chicago.
Investigators say they have proof the fire was deliberately set. A source told the Times traces of a substance used to help spread the fire have been discovered.