Hundreds of people were allowed to return home Friday as firefighters gained ground against a 20,000-acre wildfire that cast such a smoky haze over the city that drivers turned on their headlights in the middle of the day.

The blaze on the Los Angeles-Ventura county line was 20 percent contained, and was expected to be 35 percent surrounded by day's end, said Los Angeles County Deputy Fire Chief Mike Bryant.

"We're really happy with the weather today. This is a good opportunity for us," Bryant said. "It is a very, very important day for us in fighting this fire."

Firefighters were aided by fading desert winds that let more humid ocean air move back inland. But the shift also pushed smoke over parts of Los Angeles (search) and neighboring valleys, triggering health warnings.

At one point on Thursday afternoon, motorists drove through the San Fernando Valley (search) with their headlights on. On Friday, health officials urged residents to restrict outdoor activities and advised people with heart and lung diseases to take precautions.

Downtown Los Angeles bank employee Jolie Gorchov, 40, said the bad air was giving her headaches. "I don't close my windows because it doesn't make a difference," she said. "The air is so thick and smoky you can taste it."

Evacuation orders were lifted in all areas. By Friday afternoon, 40 people remained in one of the two evacuation centers that still were open.

Despite the fire's furious pace over the previous two days, the flames destroyed just one single-family home, three outbuildings, one storage building and one detached garage, authorities said.

Some 3,000 firefighters from agencies throughout the state were on the lines, aided by six retardant bombers and 11 water-dropping helicopters.

The fire erupted Wednesday afternoon in the Chatsworth area of northwest Los Angeles and was rapidly spread by strong winds.

Elsewhere, 1,200 people were evacuated from mountain communities 70 miles east of Los Angeles because of a 450-acre blaze in the San Bernardino National Forest. A small fire slumbering in hills above suburban Burbank also awakened, sending up a towering plume at midday.