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Mark Rightmire, Associated Press
A plume of smoke rises into the sky as a wildfire burns in the Cleveland National Forest in eastern Orange County, while traffic moves along a freeway through Tustin, Calif. on Friday, Sept. 12, 2014.

SANTA ANA, Calif. — Flames chewed through brush in Southern California's Cleveland National Forest and sent up a huge column of smoke Friday, but authorities did not order evacuations and said no homes were immediately threatened by the blaze.

The fire in Orange County's Silverado Canyon covered nearly 2 square miles, or about 1,200 acres, and firefighters had none of it contained, said Capt. Larry Kurtz, a spokesman for the Orange County Fire Authority.

There was little wind, but potentially record-breaking temperatures in the 90s and steep terrain made battling the blaze more difficult, he said. It's expected to be hotter Saturday, with a high of 102.

No one was forced to leave their homes, but a voluntary evacuation was announced for about 15 to 20 residences closest to the blaze. Kurtz said the fire was burning away from those areas.

"All the homes are located at the bottom of the canyon, and the fire is burning up and away from them," he said. "We're not banging on doors saying, 'Get out!'"

Firefighters hoped to gain the upper hand on the fire burning up the canyon walls by dousing the flames with water drops and digging fire lines behind ridgetops, Kurtz said.

"Because of the drought and the angle of the fuels, fire just races up canyon walls very, very fast. But when it reaches the ridgetop of these canyons, fire activity is going to decrease significantly, and that's when we're going to attack," he said. "We're going to stop this fire at the ridgetop."

Nearly 300 firefighters and four water-dropping helicopters were on scene, Kurtz said.

Silverado Canyon Road was closed to all traffic to allow emergency vehicles to pass. A portion of Santiago Canyon Road had been closed but reopened later Friday.

Cleveland National Forest sprawls over the rugged peaks of the Santa Ana Mountains straddling the Orange and Riverside county line southeast of Los Angeles.