The fire is still burning within the containment line in a hilly grass and woodland area near Steele Canyon and Capell Valley roads in unincorporated Napa County, and crews will remain at the site all day.
California Highway Patrol Officer Randall Wayne said the fire started when a 17-year-old American Canyon boy lost control of his 2003 Honda on northbound Steele Canyon Road around 6:50 p.m. Sunday.
The teen was traveling at about 60 mph when failed to negotiate a curve, ran off the road and struck an embankment, Wayne said.
The Honda rolled once and came to rest upright. The crash ignited the grass on the road's shoulder, Wayne said.
The teen and a 15-year-old Napa girl suffered minor abrasions and complained of pain, and were taken to Queen of the Valley Medical Center in Napa, Wayne said.
The CHP is investigating whether the teen was racing another car, Wayne said.
Dispatcher Jennifer Neal said more than 100 firefighters from Cal Fire and the Napa County Fire Department helped battle the blaze. No injuries related to the fire were reported.
There are homes and ranches in the area but no structures have burned, Neal said.
A second dispatcher estimated it could be days before the fire is completely extinguished.