Investigators have identified two separate "points of origin" where they believe the fire was set, CBS News has learned. FBI agents secured the scene to "maintain its integrity."
The Santiago Fire has burned about 19,200 acres east of Irvine, officials said, and it is around 30 percent contained. Six homes and eight outbuildings have been destroyed, with another eight homes and 12 outbuildings damaged. Four firefighters have been injured fighting the blaze and about 3,000 people evacuated.
In San Bernardino County, a man suspected of starting a small fire was arrested and another man was shot to death by police after he fled officers who approached to see if he might be trying to set a fire.
Meanwhile, the relentless Santa Ana winds have slowed, allowing dozens of aircraft to douse the burning hills with water, reports CBS Evening News anchor Katie Couric.
Wind was reported blowing at a sustained speed of 21 to 36 mph in some areas Wednesday, considerably less than the gusts of up to 100 mph earlier in the week.
Property damage has reached at least $1 billion in San Diego County alone, and President Bush signed a major disaster declaration for California. The president is scheduled to visit the region Thursday.
The death toll from the most recent blazes may rise as fires continue to burn and authorities return to neighborhoods where homes turned to piles of ash, but displaced homeowners and authorities were relieved that early reports were so low.
The San Diego County medical examiner officially listed six deaths connected to the blazes, but he included five who died during the evacuation who were not directly killed by the fire.
There have been at least 66 injuries, including 40 firefighters.
That contrasts to 22 dead from a fire of similar magnitude in 2003. And while the final toll has yet to be tallied from this week's fires, officials were crediting an automated, reverse 911 calling system that prompted the orderly evacuation of more than half a million people - 10 times the number evacuated four years ago.
"They are more determined that people leave," said Steve Levstik, who got his call 15 minutes before flames swept through his Rancho Bernardo neighborhood.
"It was very intense. On the call, it was like, 'This area, go! This area, go!' In 2003 there was less guidance. It was like, 'Just pay attention to the news and if it looks bad, leave.'"
But over 26,000 more homes across Southern California are still in danger, reports Couric. The wildfires have already consumed 700 square miles and forced the greatest evacuation California has ever seen.
And none of the major fires is contained, reports Couric. In many places firefighters are feeling frustrated, beating down the flames in one spot only to watch them pop-up someplace else.
"Clearly, this is going to be a," Ron Lane, San Diego County's director of emergency services, told reporters during a news conference.
The improving weather allowed for a greater aerial assault on the flames and helped firefighters beat back the most destructive blazes. Helicopters and air tankers dropped 30 to 35 loads of water on two fires that have burned hundreds of homes in the San Bernardino Mountains, near Lake Arrowhead.
"They're taking it down considerably," said Dennis Bouslaugh of the U.S. Forest Service.
Authorities said they had largely contained many of the fires north of San Diego, and all five fires in Los Angeles County were about 50 percent contained or more.
Despite the progress, none of the six major blazes in San Diego County was more than 15 percent contained, and those fires threatened more than 8,500 houses. The top priority was a fire in San Bernardino County that threatened 6,000 homes and continued to rage out of control.
So far, this week's fires have destroyed about 1,500 homes and burned 674 square miles across five counties, from Ventura in the north all the way into Mexico.
Terry Dooley, who was ordered out of his home with his wife and three sons Monday, said authorities learned important lessons from Hurricane Katrina and the 2003 California fires that wiped out 3,640 homes and blackened 750,000 acres during a two-week period.
"They learned how to get things done more quickly," Dooley said as he waited at a roadblock Wednesday to return home to San Diego's upscale, densely populated Rancho Bernardo area.
In addition to the reverse-911 system, authorities also shut down schools, halted mail delivery and urged people to stay home and off the roads if they were not in danger.
Another factor separating these fire from other disasters has been wealth. Unlike many of the poor neighborhoods flooded by Hurricane Katrina, the hardest-hit areas in California were filled with upscale homes, with easy access to wide streets. Less wealthy areas - including rural enclaves and horse farms that stretch through the mountains east of San Diego - benefited from easy road access and small crowds.
On Wednesday, about two dozen people gathered at a police barricade in Rancho Bernardo, which was one of the hardest-hit areas, hoping to retrieve medications and belongings - or simply to see if their homes were intact.
What awaited many was an apocalyptic scene: entire streets leveled, cars reduced to charred hulks of metal, homes with only chimneys left standing. House after house, 29 on one street alone, were reduced to piles of blackened concrete, twisted metal and white ash.
At one point, police officers lifted a barricade into the neighborhood only to turn residents away several hundred yards down the road at a second barricade. Some of the homeowners cursed at the officers.
"You let us in just to send us back out," one angry man yelled from his car.
Dooley knew his home was OK because his home answering machine still worked.
Six of San Diego County's 42 evacuation centers were full Wednesday but there was plenty space at Qualcomm Stadium, home to the NFL Chargers, where. People rested on cots that lined covered walkways circling the bleachers and quietly as National Guard troops watched. There were no bathroom lines.
Some displaced homeowners complained that the evacuations went too far.
Ron Morris, 68, saw smoke but no flames when he was ordered to leave a motor home park in Ramona, northeast of San Diego, Sunday night. He drove his recreational vehicle to Qualcomm Stadium's parking lot.
"It's good that everyone got out, but they did it too early in my opinion." he said.
Authorities made no apologies.
"One happy consequence" of the 2003 fires is that people remember that fire can be very unpredictable, Homeland Security Secretary Michael Chertoff said.