(CNN) -- Firefighters in southern California have contained 65 percent of a massive wildfire that has burned more than 8,000 acres, officials said Thursday.
Fifteen fire engines, 10 helicopters and 34 fire crews worked to contain the fire in Kern County, California, according to an official update.
Crews were also in place to protect homes and other structures along with air support.
On Wednesday, Gov. Arnold Schwarzenegger declared a state of emergency in Kern County.
About 1,500 firefighters were battling the blaze, a Kern County Fire Department spokesman said.
The fire has destroyed at least one home, threatens many more and prompted evacuations, the governor's office said.
The declaration orders "that all agencies of the state government utilize and employ state personnel, equipment and facilities for the performance of any and all activities" as coordinated by emergency management officials.
About 250 structures are threatened, including homes and 100 outbuildings, U.S. Forest Service spokesman Lee Bentley said.
Four injuries, all minor, have been reported. Smoke is affecting elderly residents, Kern County fire spokesman Sean Collins said.
For firefighters, steep ground and the active fire were major concerns, officials said. Air resources continue to play a key role in keeping the fire away from high risk areas, according to Thursday's update.
The exact number of people who have evacuated was not immediately known, but Bentley said that 27 people spent Tuesday night on cots and 12 others stayed in various RVs at a shelter site. Two others were at a second shelter, he said.
Kern County officials were trying to estimate how many people have left their homes.
"We did a reverse 911 call to the area affected. I'm waiting to hear back how many residences that went out to," Kern County spokesman Sean Collins said. "That's not to say that's how many people were evacuated, but it will give us an idea."
The fire broke out Sunday west of Bodfish, about 100 miles north of Los Angeles. Authorities are investigating the cause. Arson is suspected, Bentley said.
CNN's Nick Valencia contributed to this report