A fire was reported shortly after 3:30 p.m. near the eastbound Manuel T. Freitas Parkway onramp to southbound Highway 101.
When firefighters responded, they realized a series of about six spot fires along the road was burning grass, shrubs and even some trees, Gray said.
Firefighters quickly attacked the blazes and were able to get them under control, but they expect to remain at the scene for several more hours making sure they are out, Gray said.
The highway was closed in both directions for about 10 minutes, Gray said, because smoke was blowing across the roadway and causing a hazard.
The road has since been reopened, he said. No injuries were reported.