At about 5:15 a.m., a vehicle apparently somehow sent sparks toward roadside vegetation and ignited the fire, CHP Officer Kevin Kroncke said.
The No. 4 southbound lane of the highway, from Freitas Parkway to North San Pedro Road, was closed as firefighters put out the fire and then monitored the area for hotspots.
The Freitas Parkway on-ramp to southbound Highway 101 was also temporarily closed. All lanes were reopened by about 7:15 a.m.
A Sig-alert was issued for the highway at 5:30 a.m. and then canceled at 7:13 a.m.