The fires were reported at about 10:45 a.m. near the Crystal Springs Road off-ramp from southbound Highway 280, CHP Officer John Short said.
The blazes, which burned along a quarter- to half-mile stretch, were apparently sparked by a car fire on the side of the road, Short said.
The fires were extinguished by about 11:30 a.m., but firefighters from Cal Fire remained in the area this afternoon and "are making sure it doesn't come back up," Short said.
Investigators are also trying to determine what caused the car to catch fire, he said.
The emergency response initially blocked the two right lanes of the highway as well as the off-ramp to Crystal Springs Road, according to Short.
The off-ramp reopened at about 11:35 a.m., but the two lanes are expected to be closed until at least 3 p.m., he said.