A brush fire erupted Tuesday at about 4:04 p.m. when a tractor-trailer carrying hay caught on fire on northbound Interstate 5 north of Templin Highway.
The hay bales caught fire and ignited the brush on the west side of the freeway, according to the California Highway Patrol.
As of 4:40 p.m. the fire was burning uphill in 4- to 5-mph winds and had grown to 5 acres.
No structures are reported to be threatened. The fire is on U.S. Forest Service land.