Updated

The unpredictable flames burning in the Angeles National Forest are staying one step ahead of firefighters, as a flare-up on the northeast corner delayed efforts to burn out brush above the foothill cities of the San Gabriel Valley.

Incident Commander Mike Dietrich said 30-40 mph winds and 10 percent humidity Monday forced firefighters to cancel their plan to burn a line on the southern flank to protect communities from Azusa to Pasadena.

Dietrich says fighting the Station fire has cost $57.6 million to date.

Los Angeles County Fire Deputy Chief Mike Bryant says letters from grateful residents help to keep the firefighters going and bolster their spirits to fight against the ferocious fire that claimed two firefighters' lives last week.

U.S. Forest Service spokesman Nathan Judy said the weather didn't cooperate and the aircraft needed to support and monitor the burnout operations were diverted to the fire's northeastern flank.

The blaze was 56 percent contained and had blackened 157,220 acres, or 246 square miles, as it burned deeper into the wilderness in its 13th day, feeding off leaf litter on the ground, old growth and dead timber.

"Even the mountain goats won't climb in there because it's so steep and rugged," Judy said.

The flames have reached the bottom of the south face of Mount Waterman, which has a small ski area on its northern side.

Meanwhile, Los Angeles County sheriff's and fire investigators continued their homicide investigation into the fire. Officials have said the cause of the fire was arson but have released no findings.

Los Angeles County firefighters Tedmund Hall and Arnaldo Quinones were killed in a vehicle accident Aug. 30 while seeking an escape route for their inmate fire crew after flames overran their camp on Mount Gleason.

Sheriff's spokesman Steve Whitmore said the men's vehicle was airlifted off a mountain and taken to a secure location Monday so investigators could analyze it. The examination of the site where the fire started near the Angeles Crest Highway wrapped up Monday, he said.

Fire spokesman David Ortiz said a firefighter fell and had to be airlifted out Sunday night, bringing the total number firefighters injured on the Station fire to 11.

Fire spokesman David Ortiz said 19 helicopters and eight fixed-wing aircraft are fighting the blaze. Plans to airlift hand crews into rugged parts of the San Gabriel Wilderness were also scaled back.

Damage assessment teams counted 78 homes, two commercial buildings and dozens of outbuildings destroyed by the flames. Battling the Station fire has cost about $50 million, and full containment is estimated for Sept. 15.

The temporary city that sprang up to house, bathe and feed about 4,600 firefighters will be relocated from a large park in the Lake View Terrace neighborhood of Los Angeles to another park near Irwindale to the east, closer to the active fire, officials said Monday.