SANTA MARIA, Calif. (AP) — A massive wildfire is churning through Los Padres National Forest in central California, threatening hundreds of homes after injuring at least three people, authorities said.

The Gifford Fire spans more than 100 square miles (259 square km) of Santa Barbara and San Luis Obispo counties, with just 3 percent containment, according to a Monday incident update.

The blaze grew out of at least four smaller fires that erupted Friday along State Route 166 between Santa Maria and Bakersfield, said Flemming Bertelson, a spokesperson for the U.S. Forest Service.

“That gave us multiple fronts, and the flames started fanning out in many directions,” he said Monday. “The fire is gobbling up chapparal and brushland and running up very steep slopes.”

The highway is closed in both directions east of Santa Maria.

More than 450 structures are under threat. Ranchers evacuated cattle as aircraft made water drops on the encroaching flames.

A motorist was hospitalized with burn injuries after getting out of his vehicle and becoming overrun by flames, Bertelson said. Two contract employees assisting firefighters were hurt when their all-terrain vehicle overturned.

More than 1,000 firefighters working in hot and dry conditions are scrambling to make progress against the blaze before so-called sundowner winds whip up around dusk. The National Weather Service says erratic afternoon gusts could reach 25 mph (40 kph) in the fire area.

The causes of the fires are under investigation.