A fast-spreading wildfire on the edge of a major freeway in California’s Central Valley has prompted evacuation orders for a handful of homes in the foothills southwest of Tracy.

The Corral Fire started around 3 p.m. along Corral Hollow Road in San Joaquin County, on land operated by the Lawrence Livermore National Laboratory’s Site 300, a facility that helps develop explosives material and other ordnance.

As of 7 p.m., the wildfire has torched nearly 5,000 acres of grass vegetation, according to Cal Fire’s Santa Clara unit, which said the fire was 40% contained.

Flames stoked by winds pushed the fire east, prompting the San Joaquin County Office of Emergency Services to issue mandatory evacuations for zones SJC 210 and SJC 211, as well as evacuation warnings for SJC 215. The area about 5 miles south of downtown Tracy is sparsely populated with ranch homes and other farmland.

Several aerial firefighting resources have responded to the blaze after flames jumped a control line. Crews from the Alameda County Fire Department and South San Joaquin County Fire Authority are also at the scene, Cal Fire said.

Fire officials say previous prescribed burns to the west are helping to stop the spread, but the fire is moving east against Interstate 580 on a portion of major freeway connecting I-5 to the Altamont Pass area and the Bay Area. The burn area is about a mile north of the Tracy Golf & Country Club where I-580 and I-5 split.

I-580 is closed in both directions between Corral Hollow and Vernalis roads, according to officials.

An evacuation shelter has been opened at the Larch Clover Community Center, 11157 W. Larch Road, in Tracy.

The cause of the fire is under investigation.