With one of the largest wildfires in Southern California history nearly half contained, authorities were pressing forward with their investigation to try and determine who set the deadly blaze.

The fire, which started Aug. 26, has killed two firefighters, blackened 242 square miles of Angeles National Forest and destroyed at least 76 homes. Fire agencies so far have spent $43.5 million fighting the fire.

At least a dozen investigators were working Saturday to analyze clues found at a burnt hillside near Angeles Crest Highway — the place where fire started more than a week ago. But officials, who say the cause of the fire was arson, were hesitant to release any of their findings to the media.

"Arsonists are not stupid. They can read," said U.S. Forest Service Cmdr. Rita Wears, who supervises federal agents investigating the fire. "I have to be very careful."

The fire was 49 percent contained Saturday night after crews built protective lines on the northwestern flank near Santa Clarita, said incident commander Mike Dietrich. Still, two new flare-ups presented challenges.

The fire jumped a dozer line near the closed Angeles Crest Highway and burned about 500 new acres in the Pleasant View Ridge Wilderness Area, Dietrich said. Flames were within about five miles of the community of Juniper Hills and firefighters planned to make the area their primary focus into the night.

Dietrich said crews also were fending off new fire activity on the southeastern end of the fire and trying to keep the blaze from burning into Santa Anita Canyon and Chantry Flats north of Arcadia and Monrovia.

And firefighters were trying to slow the eastern movement into the San Gabriel Wilderness and secure the southeastern flank north of Arcadia, Monrovia and other foothill communities.

No homes were immediately threatened in either area, said.

"We're making tremendous progress," Dietrich said, "but we have not turned the corner on this fire."

The weekend weather forecast called for cooler temperatures and slightly higher humidity that could help firefighters further surround the blaze. Because of the reduced heat, about 400 firefighters assigned to protect structures had been dismissed, Dietrich said. About 4,800 firefighters remained.

Near a large shade tree where crews get their daily briefings, a makeshift memorial was set up for fallen Los Angeles County firefighters Tedmund Hall and Arnaldo Quinones.

Capt. Hall and Specialist Quinones were killed Aug. 30 while seeking an escape route for their inmate fire crew after flames overran their camp on Mount Gleason. The two died when their truck plunged 800 feet off a steep mountain road.

Sheriff's detectives opened a homicide investigation after the fire was ruled arson earlier this week, and Gov. Arnold Schwarzenegger has offered $100,000 for information leading to the arrest and conviction of the culprit.

"We are in the early stages, just beginning to put things together," said sheriff's Lt. Liam Gallagher, who is heading the homicide investigation. "Firefighters losing their lives in the line of duty is an added incentive, but we work every case to the fullest."

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