SAN ANDREAS -- Investigators now believe they know what started the Willow Fire burning in Calaveras County.
The California Highway Patrol arrested a woman for reportedly driving with a flat tire, which created sparks that started the blaze.
"A vehicle driving down the road on a flat tire with a shower of sparks coming out behind it," said Officer Toby Butzler, a spokesperson for the CHP.
Butzler said the driver, 44-year-old Renee Hogan, was oblivious to what her car was doing -- starting a dozen spot fires along Mountain Ranch Road. A good Samaritan had to intervene.
"Eventually a person behind the car tried to get her attention, couldn't for whatever reason, got around her, blocked the car with his vehicle that made her stop basically," Butzler said.
Butzler told FOX40 Hogan didn't even realize her own car was on fire, as the good Samaritan had to rescue her.
"Pulled her out of the car and kind of told her her car's on fire, she didn't know," he said.
Hogan was arrested for allegedly driving on a suspended license and driving under the influence. Butzler said she was allegedly on pain pills and cannabis.
From inside the Calaveras County Jail, Hogan decline to speak to FOX40. But Cal Fire investigators will also be charging her with six additional charges for allegedly starting the 450 acre Willow Fire, which was just 30 percent contained as of Monday afternoon.
"The crews are out there improving the lines, mopping up all the hot spots, making sure everything is out around the homes," Cal Fire Division Chief Roy Evan said.
Hogan is expected to appear in court Tuesday for her arraignment.
According to Butzler, Hogan is homeless, believed to have been living inside that car. She does have prior arrests, according to Butzler.