A fire in the Sacramento region spread to about 4,000 acres by late Saturday, while a blaze that began in the afternoon around Yosemite National Park threatened a small community.

The so-called Sand Fire began Friday in the Sierra Nevada foothills and has since spread through more than six square miles of drought-stricken grasslands east of Sacramento.

Fire crews battled the two wildfires that threatened many homes and forced hundreds of evacuations, officials said.

The blaze, which has burned five homes and seven outbuildings, led to evacuation orders covering about 515 homes in and around the River Pines Estates community in Amador County.

“The fire’s moving in and around homes in the area,” said Lynn Tolmachoff, a spokeswoman for the California Department of Forestry and Fire Protection. “The leading edge is bumping up against residences as we speak.”

The fire was only 20 percent contained by nightfall, despite efforts by 1,464 firefighters and aircraft that included a DC-10 air tanker.

The Sand fire blazed through forests and homes in El Dorado and Amador counties and forced hundreds of people to flee their homes with only minutes of warning.

A vehicle driving over dry vegetation caused the fire, said Chris Anthony, a Cal Fire spokesman, late Saturday.

Early in the day, officials were saying 750 people had been displaced by the fire, but by Saturday afternoon another 450 homes were ordered evacuated. The evacuation center for residents was moved from the fairgrounds to larger quarters at Ponderosa High School in Shingle Springs where American Red Cross spokesman David Kennedy said as many as 400 people were expected.

Anthony said firefighters were dealing with tricky, steep terrain.

In addition to the firefighters, helicopters and small planes, a DC-10 air tanker could be seen flying repeated missions overhead. One observer watched the DC-10 drop four loads of retardant in a four-hour span.