A wildfire threatening thousands of homes in Southern California spread slowly through scenic canyonlands, straining resources as crews struggled to contain hundreds of other blazes around the state. "The firefighters are stretched thin, they are exhausted," and some have gone days without sleep, said Gov. Arnold Schwarzenegger, who visited a command post Saturday in Santa Barbara County. A slew of wildfires, most ignited by lightning two weeks ago, has burned more than 800 square miles of land throughout California. The blazes have destroyed at least 69 homes and other buildings and contributed to the death of a firefighter who suffered a heart attack while digging fire lines. About 1,400 fires have been contained, but more than 330 still burned out of control Saturday. Schwarzenegger said the state's top priority was in the coastal region of Santa Barbara County, where nearly 2,700 homes were threatened by a four-day-old fire in the Los Padres National Forest that has consumed about 13 square miles. Cooler, moist air Saturday kept the fire sluggish and helped firefighters trying to surround it, said Pat Wheatley, county spokeswoman. Evening fell without the return of the late afternoon "sundowner" winds that had sent flames racing up to homes on Friday evening, she said. The fire was 24 percent contained, she said. More than 2,600 homes were under mandatory evacuation Saturday, and residents in another 1,400 were warned to be ready to flee if the flames gathered speed. Wheatley said the mandatory evacuation orders were partially lifted later Saturday, allowing many residents to return home, but she did not know how many homes were affected. The fire, which was burning in 15-foot-high, half-century-old chaparral, still had the potential to roll through a hilly area of ranches, housing tracts and orchards between the town of Goleta and Santa Barbara, keeping firefighters on their toes. Nearly 1,200 firefighters struggled to surround the blaze while a DC-10 air tanker and other aircraft dumped water and fire retardant along ridges and in steep canyons. Investigators think the fire, which began Tuesday, was human-caused. The US Forest Service on Saturday asked for public help in determining who set it and whether it was sparked accidentally or on purpose. Meanwhile, cooler weather helped crews attacking a two-week-old blaze that has destroyed 22 homes in Big Sur, at the northern end of the Los Padres forest, but the fire continued to grow slowly on all flanks Saturday night. The fire, which had blackened more than 110 square miles was only 5 percent contained with full containment not expected until the end of the month, but morning fog that moved in from the sea helped prevent it from advancing on Big Sur's famed restaurants and hotels. A homeowner near Big Sur was arrested Friday after officials said he refused orders to stop setting his own backfires.