California Investigators Search for Cause of Deadly Wildfires

Several of the 10 blazes sweeping through roughly 20,000 acres north of San Diego were slowly coming under control as cooler temperatures and calmer winds aided emergency crews working around the clock. Fleets of water-dropping helicopters and thousands of firefighters were preparing for renewed battles Saturday morning.

Thousands of evacuated residents were able to return home in some areas and police ramped up their efforts to find out how so many wildfires began within hours of one another during an uncharacteristic time of year, NBC News reported.

As of late Friday the fire in Carlsbad, one of the worst-affected areas, was 90 percent contained and the massive Cocos fire in San Marcos was 50 percent contained.

A 57-year-old man has already appeared in court charged with arson in connection with one of the smaller fires in Oceanside, which started Wednesday.

Alberto Serrato pleaded not guilty and bail was set at $250,000. Witnesses said they saw the man adding dead brush onto smoldering bushes in the San Luis River bed which further ignited them, but police do not believe he was the original instigator.

"Unfortunately we don't have the guy that we really want," Oceanside police Lt. Sean Marshand said.

Two other people were arrested in the Escondido area on suspicion of attempted arson after they were setting off two small fires which were extinguished within minutes.

Isaiah Silva, 19, was held on $50,000 bail. Details of the second person were withheld because he or she is 17 years old and a juvenile.

There is no evidence their actions were linked to the wider wildfires but with many of the fires igniting within close time proximity Wednesday, officials wonder if some were deliberate.

"Do people have suspicions? Yes," said Carlsbad Police Capt. Neil Gallucci. "But can we confirm them? The answer is no."

Police are speaking to people who have called a tips hotline and will be looking for suspicious footprints or tracks.

Yet there could also be a far less ominous cause. This season has seen unseasonably dry weather, strong 50 mph Santa Ana winds and high temperatures in the 90s. In these conditions, fires can be ignited by car sparks, construction equipment, a discarded cigarette or power cables.

"Our investigation might be over quickly for some of these fires — say, if we find a piece of metal nearby from a catalytic converter that back-fired," San Diego County Sheriff Bill Gore said. "But others might not be so easy to determine. We'll be talking to people in the areas to see if they saw anything to see if arson might have had a role."

One of the newest fires broke out late Thursday near the Marine Corps' Camp Pendleton, forcing the evacuation of three sections within the giant base.

Three separate blazes in that area were still raging fiercely late Friday. A firefighter from the military base, roughly the size of Rhode Island, suffered heat exhaustion helping to battle the flames.

The charred body of a man was also discovered in a homeless encampment near Carlsbad, local officials said.

In total, the fires are estimated to have caused more than $20 million in damage and forced tens of thousands of residents to evacuate their homes.

Schools, a college campus and amusement park Legoland were all shuttered and graduation ceremonies cancelled.

Hillsides have turned black, billowing smoke caused health warnings to be issued across much of Southern California and several homes and vehicles have been completely destroyed.

Despite the progress made by firefighters tackling the Cocos Fire in San Marcos, more than 1,500 structures there remained at risk, officials said.

The worst fire in California's recent history occurred in central San Diego County in 2003, when more than 437 square miles were scorched, nearly 3,000 buildings were destroyed and 15 people were killed.