Authorities blocked access to the crime scene, a scorched area of scrub and trees off the side of the Angeles Crest Highway, as they analyzed clues including incendiary material reported to have been found there. Authorities say the fire was arson, but are still trying to find a culprit and understand how it was set.
"We are going to find out what we can and present it to the D.A.," said Los Angeles County sheriff's Lt. Liam Gallagher, who is heading the homicide probe and whose investigators worked through the night into Friday. "We are considering it a murder investigation."
Gallagher said as many as 14 investigators would be on hand to help with the probe over the weekend.
"We are in the early stages, just beginning to put things together," he said. "Firefighters losing their lives in the line of duty is an added incentive, but we work every case to the fullest."
The fire has burned through 241 square miles of the Angeles National Forest. More than 70 homes have been destroyed.
Gov. Arnold Schwarzenegger offered a $100,000 reward for information leading to the arrest and conviction of whoever set the blaze. The figure is the maximum the chief executive can offer under California law.
Also Friday, authorities said that several firefighters were exposed to cyanide gas in two separate incidents as they were mopping up hot spots near the small city of Acton on the northern edge of the massive blaze.
Deputy Incident Commander Carlton Joseph said four firefighters developed respiratory problems on Tuesday and one was still hospitalized on Friday.
Joseph said that on Thursday six firefighters were digging at a patch of smoke near the first incident when they smelled a sweet odor, like plastic burning, and were briefly hospitalized with respiratory problems.
A hazardous materials team found no evidence of dumping and believe the cyanide possibly came from old mining operations, Joseph said.
Arson investigators have plenty of experience to draw upon as they try to figure out who ignited a fire that torched more than 240-square-miles of the Angeles National Forest on the edge of Los Angeles and burned 76 homes. The cost of fighting the fire was estimated at $37 million so far.
Most wildfires are caused by human activity, and government statistics show that people were faulted for 5,208 wildfires in Southern California in 2008, the highest number since at least 2001. Between 2006 and 2008, Southern California was the only region of the country to see a significant jump in the number of wildfires blamed on people.
Still, very few of the forest fires lead to criminal or civil cases. The U.S. Forest Service recorded nearly 400 arson wildfires since 2005, records show.
Firefighters paused in their battle against the fire Friday to pay their respects to two fallen comrades whose deaths have triggered the investigation.
Hundreds of weary firefighters who have slogged on the front lines for the past 11 days took off their caps and helmets and bowed their heads at a tribute for Capt. Tedmund Hall and Specialist Arnaldo Quinones, held before dawn at the command center in the foothills near the flames.
The men helped save about 60 members of an inmate fire crew Sunday as flames approached their camp by setting a backfire that allowed the group to get to safety, said Los Angeles County Fire Capt. Glenn Goulet. The pair died when their truck plunged 800 feet down a steep mountain road.
The blaze was 42 percent surrounded Friday, authorities said. Investigators will pick through clues at the scene, try to establish a likely motive for the arsonist, then predict the characteristics and traits of the unknown offender as they look to make an arrest.
Timothy Huff, a former profiler with the FBI who has interviewed more than 100 convicted arsonists, said the typical profile of an arsonist is that of a white man aged between 15-25. The most common arson motivation is revenge, Huff said, with offenders seeking to harm individuals, groups, institutions or society in general.
Riverside County Deputy District Attorney Michael Hestrin, who has prosecuted wildfire arson cases, said it depends what kind of evidence investigators gather in the current fire to make a decision to file murder charges.
"An arsonist could be responsible for all the consequences that his act set in motion," Hestrin said. "He unleashes this disaster and men died in an effort to save people from ruin or injury. He could be liable for those deaths."
Firefighters have set up a makeshift memorial for the fallen firefighters at the base camp. An American flag and a trio of firefighters' tools were flanked by photos of the firefighters -- smiling in uniform -- and surrounded by wreaths. Nearby, firefighters had scribbled messages on sheets of paper tacked to a large wooden board.
"God bless you brother," one had written. "Never forgotten," wrote another.
Those who knew Hall, 47, and Quinones, 35, said they were both motorcycle enthusiasts who were devoted to their jobs. Quinones was eagerly awaiting the birth of his first child and had recently turned down a work assignment, Goulet said.
"He said 'Hey, my baby's coming. I want to be there.' So he stayed at camp," said Goulet, who added Quinones had a motto on the back of a tattoo that said, "First in, last out."