LOS ANGELES — Fresh firefighting crews were brought in Monday to help battle the huge wildfire charging through the coastal mountains of Santa Barbara County, one of more than 300 active blazes across California.

Some evacuees started returning home to the area 100 miles northwest of Los Angeles.

With a heat wave forecast this week, firefighters on the blaze in the Los Padres National Forest tried to take advantage of Monday morning marine fog and a last day of moderate weather, said Stanton Florea, spokesman for the U.S. Forest Service.

Officials brought in five "hot shot" crews from Arizona and New Mexico, a total of 100 firefighters who were being dropped by helicopter in the Santa Ynez Mountains or sent hiking in to thin brush and slow the fire's progress, Florea said.

"They're going to try to create a line around the western end," he said.

Other crews were setting backfires to burn brush so there is no fuel for flames to feed on.

"There's a window we can do some of these firings in," Florea said.

The fire had blackened about 15 square miles of the national forest above the city of Goleta, in southern Santa Barbara County, since starting July 1. It was 35 percent contained Monday morning, Florea said.

Many residents started to return Monday after most mandatory evacuation orders were lifted. Some warnings and mandatory orders remained in effect in scattered mountain communities.

Officials did not have the number of homes currently affected. At the height of threats to Goleta-area communities, residents of nearly 2,700 homes were told to leave or warned to be ready to flee.

A weekend break in summer heat had allowed firefighters to largely extinguish flames on the southern end of the blaze, where most of the threatened residential areas were.

However, the cooler weather is forecast to give way to 90-degree heat and low humidity this week.

"There's a heat wave setting in," said Jim Andrews, senior meteorologist for AccuWeather.com. "Today is still kind of a transition but it will set in in earnest tomorrow."

Investigators believe the fire was human-caused.

Wildfires have blackened more than 800 square miles and destroyed at least 69 homes throughout California, mainly in the northern part of the state, in the past two weeks. One firefighter died of a heart attack.

Sunday's cooler weather also helped firefighters advance on the 2-week-old blaze that has destroyed 22 homes in Big Sur, on the coast at the northern end of the Los Padres forest.

"The fog held on a little bit stronger than was originally anticipated, which was great for the crews out working on the lines," said Sarah Gibson, a spokeswoman for the fire command post.

The improved weather in the Big Sur area had drawbacks. Fog made it more difficult for firefighting aircraft to take off and hampered efforts to start controlled burns to clear brush out of the path of the advancing wildfire, Gibson said.

The fire has charred 117 square miles in the Big Sur area and was just 11 percent contained Monday. Officials said crews were burning out brush between the fire's leading edge and Big Sur's famed restaurants and hotels and cutting more lines to block flames creeping down from ridge tops.

"The biggest challenge is whether or not the containment lines that they're building now and continuing to improve are going to hold as the fire approaches," said Rolf Larsen, a spokesman for the U.S. Forest Service.

California's siege of fires began with an extraordinary lightning storm in late June. According to state figures, about 1,450 fires have since been contained, but more than 330 were still out of control Monday morning.

Gov. Arnold Schwarzenegger issued a health warning, urging people affected by smoke to stay inside and limit their physical activity. Last week, he ordered 400 National Guard troops trained in help combat the flames.

Associated Press Writers Samantha Young in Sacramento, Christopher Weber and Robert Jablon in Los Angeles, Lisa Leff and Marcus Wohlsen in San Francisco and Amanda Fehd in Berkeley contributed to this report.