A wind-driven 16,000-acre (6,400-hectare) wildfire raced across hills and canyons along the city's northwestern edge, threatening homes and forcing hundreds of people to evacuate.
Some 3,000 firefighters aided by aircraft struggled Thursday to protect ridgetop houses along the Los Angeles-Ventura county line, a rugged, brushy landscape west of Los Angeles' San Fernando Valley. Officials said the blaze was 5 percent contained as it burned toward such communities as Thousand Oaks, Simi Valley, Calabasas and Agoura.
Numerous homes were evacuated in nine areas, and the Red Cross reported 600 people had signed up to stay at five of its shelters. Poor air quality forced California State University at Northridge to cancel classes for the day.
At least one home and five other structures were lost, but 2,000 buildings had been saved by firefighters, Los Angeles County Supervisor Zev Yaroslavsky said.
"We are guardedly optimistic, if the weather cooperates, if the public cooperates," Yaroslavsky said. "This may end well for all of us, but weather is unpredictable in these parts and everyone needs to be on guard."
Temperatures were in the high 90s Fahrenheit (mid 30s Celsius) but were expected to drop over the next few days while humidity rises.
"The winds have died down substantially and that's going to be a big advantage for us in getting control," said Los Angeles County fire Capt. Kurt Schaefer. "With the weather changing, we should start to see the containment numbers go up."
Some gusts were reported on the fire lines, but there was no reappearance of the strong winds from the interior that fanned a small brush fire into a conflagration on Wednesday.
The cause of the fire was not immediately known, reports the AP.