Flames then pushed west to the rolling grasslands of Ventura County and made runs toward Simi Valley neighborhoods of modern homes defended by a broad firebreak, helicopters, airplanes and ground crews.
The fire is one of three major blazes that have burned more than 34 square miles of Southern California, destroyed dozens of homes and forced thousands of people to evacuate their homes this week. One man died in the flames, and a motorist was killed in a crash as a fire neared a freeway.
Despite the fire's activity, there were no reports of new structural losses in the Porter Ranch area. Nineteen buildings, including some homes, were destroyed there Monday.
Ten miles away, there was major progress against Los Angeles' other big wildfire.
A 7½-square-mile blaze in the northeastern San Fernando Valley was 70 percent contained and some evacuees were allowed to go home. But people who lived in an area where 38 mobile homes were destroyed were not permitted to return.
Teresa Escamilla, 47, lay on a cot in a Red Cross shelter, thinking the worst. She believed she lost everything including a shoebox containing five years of savings.
"It feels like it's not real," the nursing assistant said in Spanish. "It's a nightmare."
Mayor Antonio Villaraigosa acknowledged the uncertainty facing residents of the fire areas.
"Many still don't know when they are going to return home," he told a news conference. "Our hearts and prayers are out with all of them."
On the north coast of San Diego County, a 3,600-acre fire at the Marine Corps' Camp Pendleton was 60 percent contained. Evacuation orders were largely lifted for about 2,000 Marine Corps personnel and family members in military housing and residents of about 1,500 homes in neighboring Oceanside.
In eastern San Diego County along the U.S.-Mexico border, a 200-acre fire that forced residents from 300 homes in the community of Campo was 70 percent contained and evacuations were canceled.
The outbreak of fires followed the weekend arrival of the first significant Santa Ana winds of the fall.
The National Weather Service said the intensity of the winds was diminishing but warned there would still be strong gusts. Warnings for critical fire weather conditions were to remain in effect until Wednesday night.
The Santa Anas usually sweep in between October and February as cold, dry air descending over the Great Basin flows toward Southern California and squeezes through mountain passes and canyons. The extremely low humidity levels, which make vegetation easier to burn, and high windspeeds combine to whip fires into infernos.
Associated Press writers Shaya Tayefe Mohajer, Solvej Schou, Robert Jablon in Los Angeles and Chelsea J. Carter in San Diego contributed to this report.