Official: L.A.-Area Blaze Man-Made

Updated at 11:35 p.m. EDT

Firefighters made more progress Wednesday against a giant wildfire that has ravaged a national forest north of Los Angeles as investigators said the blaze was human-caused and officials began letting more people back into their homes.

Officials are still trying to figure out what set off the blaze in the Angeles National Forest that had burned nearly 219 square miles, or 140,150 acres, by Wednesday.

Deputy incident commander Carlton Joseph would only say that the fire was human-caused, but it's not known specifically how it was started or whether it was accidental or arson.

Over 90 percent of California wildfires are caused by people, reports CBS News correspondent Sandra Hughes in Tujunga, Calif.

Joseph said a human cause could include a range of things from a dropped cigarette to a spark from something like a lawn mower. Joseph says investigators have several leads and notes that lightning has been ruled out as a possible cause.

Wildfire photo essay
Local coverage from CBS station KCBS in Los Angeles

Investigators huddled beneath a partially burnt oak tree Wednesday near the spot where fire started - signs that the probe is actively under way. Pink and yellow tape roped off part of a ravine next to the tree where small red flags were planted.

Firefighters have created a perimeter around 22 percent of the blaze, largely by removing brush with bulldozers and setting controlled burns. Bulldozers still have 95 miles of fire line to build, mostly on the blaze's eastern front near the San Gabriel Wilderness Area.

Hundreds of firefighters guarding foothill communities against the blaze were being sent back to their stations late Wednesday as the threat eases.

Los Angeles County fire Capt. Mark Whaling says 13 strike teams are being released Wednesday. They've been defending homes in La Canada Flintridge, La Crescenta and other communities north of Los Angeles.

About 270 firefighters will leave, along with 65 of the 500 fire engines.

Whaling says it's the first time any teams have been demobilized since the fire began seven days ago.

Gov. Arnold Schwarzenegger visited the fire area Wednesday morning and served breakfast to firefighters, scooping Cream of Wheat into paper bowls and giving them plenty of protein so "they get all pumped up for the next fight out there with those fires."

"The crews are making excellent progress based on the ," U.S. Forest Service incident commander Mike Dietrich said at a Wednesday news conference.

Since erupting Aug. 26, the blaze has destroyed more than five dozen homes, killed two firefighters and forced thousands of people from their homes.

Los Angeles County Sheriff Lee Baca said only 50 homes in his jurisdiction remained under mandatory evacuation Wednesday, down from 4,000 on Tuesday. He said that about 2,000 homes in the city jurisdiction were under mandatory evacuation orders.

At least 62 homes have been destroyed in a fire that has burned an area the size of Chicago, Hughes reports.

"I was just like, 'Oh my God, thank you so much to the firefighters, like thank you so much for saving my house,'" Lyna Avanessien, an evacuee who returned Wednesday to find her home intact, told Hughes.

Nearby, Mt Wilson, home to critical communication towers, remained under threat, despite yesterday's aggressive air assault. "The whole basin depends on this mountain, from your cell phones to your news transmission and everything in between," firefighter Vince Pena told Hughes.

Firefighters are doing what they can to defend Mt. Wilson before the flames arrive. They have burned away dry brush, but if the blaze reaches the forest canopy, the communication nerve center could explode.

Officials also were keeping a close eye on the wind, which had been calm overnight but could pick up Wednesday afternoon and move flames closer to homes and a historic observatory on Mount Wilson.

In a hillside neighborhood of Glendale, Frank Virgallito stood in a group anxiously watching a controlled burn edge toward their neighborhood.

Virgallito said he and his neighbors had been on high alert since Friday but ignored a voluntary evacuation.

"You don't sleep well," Virgallito said. "I get up every hour and a half or two hours to get a good view of where the fire is. For four days we've been a little sleep-deprived. It's unnerving."

Virgallito said he saw deer, coyote and skunks scampering down his street away from the heat and ash of the smoldering wilderness.

Officials also worried about the threat to a historic observatory and TV, radio and other antennas on Mount Wilson northeast of Los Angeles. But on Tuesday, firefighters set backfires near the facilities before a giant World War II-era seaplane-turned-air tanker made a huge water drop on flames inching toward the peak from the north and west.

By nightfall, 150 firefighters and engines were stationed at the peak to defend the towers, said fire spokesman Paul Lowenthal.

The flames crossed the Angeles Crest Highway into the San Gabriel Wilderness to the east on Tuesday, Lowenthal said. Firefighters made progress on fire breaks to the north near Acton and southwest from Altadena to the Sunland neighborhood.

Firefighters and longtime residents know it could be so much worse. Autumn is the season for the ferocious Santa Ana winds to sweep in from the northeastern deserts, gaining speed through narrow mountain canyons, sapping moisture from vegetation and pushing flames farther out into the suburbs.

"If we had Santa Anas, we still have all this open land here on the western flank and islands of vegetation would throw embers into the air, which would blow down to the homes," Fire spokesman Henry Martinez said, his voice trailing off as he imagined the worst-case scenario. "Let's hope that doesn't happen."

The wildfire season usually doesn't gather steam until the winds hit in October, but the fire has been driven by dryness instead of wind. The region is in the midst of a three-year drought, and the tinder-dry forest is ripe for an explosive fire.

Smoke billowed thousands of feet up in the air, forming what firefighters call an "ice cap," which dissipated and was pushed east for at least 800 miles.

In Colorado, smoke from the Station Fire combined with soot from local fires to block mountain views from Denver.

"That really speaks to the columns of smoke and how much burning was going on," said Norv Larson, a meteorologist with the National Weather Service in Grand Junction, Colo.

"I've put haze in the forecast. I don't see it ending anytime soon," Larson said. "We've got our fires here, you've got your fires there."

Flames charred other parts of Southern California, including one that burned at least 1.5 square miles in the San Bernardino County community of Oak Glen and another that threatened 400 homes in Yucaipa and was at 70 percent containment.

Lance Williams, 49, managed to save his aunt's home in Delta Flats, a remote community tucked in a canyon in the Angeles National Forest, but returned Tuesday to find his neighbors' homes in ashes.

"It looked like hell," Williams said. "The fire was creating its own winds. There was no way of predicting which way it would go."

He said he used a water pump to fight off the firestorm that raced down hillsides into the canyon. By the time he ran out of water, fire crews had arrived to defend the home that had been in his family since 1945.

Near the remains of house, the charred frames of animal cages swayed in a light wind. In one of the cages, the remains of three small dogs were found.

The fire also took a toll on firefighters who bunk down each night in tents at the huge fire command center. Glendale firefighter-paramedic Jack Hayes, 31, said he had not taken a day off for a week.

"You can't sleep," said Hayes, who had the beginnings of a beard and bloodshot eyes. "You're ready to go and there's always something you could be doing."

Two firefighters - Capt. Tedmund Hall, 47, of San Bernardino and firefighter Specialist Arnaldo "Arnie" Quinones, 35, of Palmdale - were killed Sunday when their vehicle plummeted off a mountain road. Quinones' wife is expecting a child soon, and Hall had a wife and two adult children.