Many people have returned home to see the extent of the fire damage
Firefighters fighting to contain a huge wildfire in mountain areas north of Los Angeles have brought it under greater control, fire officials say.
The fire was 38% contained by Thursday, up from 28% the previous day, and most residents have been allowed home.
However, firefighters are still battling to contain the south-eastern flank of the fire, which threatens communities in the foothills below.
Investigators have stepped up their inquiries into how the blaze started.
Fire officials said on Wednesday there had been no lightning reported in the area. A human cause - such as the throwing of a lighted cigarette into dry brush - has not been ruled out.
The fire covers nearly 150,000 acres and is now the largest in Los Angeles County's history, the LA Times newspaper reports.
'Change of pace'
Fire official Mike Dietrich said preventing the fire from spreading to the south-east, where it menaces areas including Pasadena, Sierra Madre and Monrovia, was now the "number one priority".
Officials said good progress had been made on Wednesday, with firefighters' efforts aided by more humid weather, but warned it could take until mid-September to contain the fire entirely.
"We're changing the pace and treating this as a marathon," Mr Dietrich said. "If it were a 26-mile race, we'd only be at mile six."
The blaze has destroyed 64 homes and left a handful of people injured. Two firefighters died on Sunday after their vehicle was overrun by flames.
Many people ordered to evacuate the area have now returned to their homes.
"It looks like nothing changed but when the sun comes up tomorrow, I expect we'll see the hills blackened and gray," Tujunga resident TJ Lynch told the Associated Press, after finding his home still intact on Wednesday.
Wildfires are a feature of the Californian summer, but it is unusual for them to break out so close to major population centres.
The latest fire is not being fanned by the Santa Ana winds that typically kick up in October. Instead, it is being fuelled by extremely dry brush that has not burned in more than 40 years.