(AP) -- The threat of wildfire reaching the Los Alamos nuclear lab and the town that surrounds it eased as crews made progress under cloud cover and rain, but concerns turned Friday to lands held sacred by a Native American tribe as firefighters braced for a hot, dry weekend.
The fire has blackened more than 162 square miles in the last six days, making it the largest fire in New Mexico history. Erratic winds and dry fuels helped it surpass the 2003 Dry Lakes fire, which took five months to burn through 94,000 acres in the Gila National Forest.
The Los Alamos National Laboratory remained closed, and fire officials said there was no chance the thousands of evacuated residents and lab employees would be able to resume their normal lives Friday.
Still, the fire chiefs in charge of battling the massive blaze were confident their crews would be able to keep flames from spreading down a canyon that leads to the lab and the town.
"The way it looks is we made good progress on that side as far as holding the fire from going any farther toward Los Alamos along the canyon," said fire information officer Rick Barton. "The guys are burning out in that area in places trying to strengthen the lines that we have established."
Los Alamos County Fire Chief Doug Tucker said the area in the canyon that was burning previously was thinned, providing a safe area for firefighters to attack the flames.
The challenge again Friday would be the weather.
"The good news is there may be less erratic winds, but it's going to be warmer and drier," Barton said. "The fire will start heating up later in the day as the moisture evaporates. Just hotter and drier."
Conditions in the area are so dry that the fire was burning downed trees that were scorched in the huge Cerro Grande fire in 2000. The fire also burned through moisture-rich aspen trees to push into the canyon.
"This is a fire like we've never seen before," Santa Clara Pueblo Gov. Walter Dasheno told The Associated Press in a telephone interview.
He said his people are devastated by the news coming in from the front lines of the firefighting efforts - cultural sites destroyed, forest resources lost and plants and animals that the pueblo's 2,800 residents depend on gone.
"We cried when we saw Mother Nature doing what she was doing to our canyon area. We were helpless," Dasheno said.
He said the tribe has discussed the possibility of evacuating the pueblo if the fire gets closer. Community meetings were being held each day to keep residents informed.
Los Alamos Canyon runs past runs past the old Manhattan Project site in town and a 1940s-era dump site where workers are near the end of a cleanup project of low-level radioactive waste. The World War II Manhattan Project developed the first atomic bomb, and workers from the era dumped hazardous and radioactive waste in trenches along six acres atop the mesa where the town sits.
"The threat is pretty limited," said Kevin Smith, the Department of Energy's National Nuclear Security Administration site manager for Los Alamos, which over sees the lab.
Los Alamos Canyon also runs through town and a portion of the northern end of the lab, where a weapons research nuclear reactor was located until it was demolished in 2003.
The fire burned upslope at least three miles from the sites and didn't pose an immediate threat. Fire had crept to within a half-mile of homes in town.
Lab officials were trying to determine the extent to which thousands of experiments at the facility have been affected by a shutdown caused by the fast-moving fire. Lab Director Charles McMillan said teams will quickly figure out how things stand as soon as they're able to return.
The lab has been closed since Monday, when the town of Los Alamos and some of its surrounding areas - 12,000 people in all - were evacuated. There was no word on when it would reopen. Tucker said Los Alamos residents won't be allowed back home until Sunday at the earliest.
Officials said the lab has some 10,000 experiments running at the same time that have been put on hold.
The delayed projects include studies on materials needed to extend the life of 1960s-era B61 nuclear bombs as well as experiments run on two supercomputers. The lab works on such topics as renewable energy and particle physics, solar flares, forensics on terrorist attacks, and studying the AIDS virus at the molecular level to help scientists develop strategies for developing vaccines.
On Monday, about an acre of lab property burned, raising concerns about possible contamination from material stored or buried on lab grounds. As a precaution, the government sent a plane equipped with radiation monitors over the lab. Samples analyzed so far from some of the lab's monitors show nothing abnormal in the smoke.
Lab authorities, along with outside experts on nuclear engineering, expressed confidence that the blaze would not scatter radioactive material, as some in surrounding communities feared.
Anti-nuclear groups sounded the alarm about thousands of 55-gallon drums containing low-grade nuclear waste - gloves, tools, even paper notes and other contaminated items - about two miles from the fire.
Lab officials said it was highly unlikely the blaze would reach the drums, and that the steel containers can in any case withstand flames and will be sprayed with fire-resistant foam if necessary.
Meanwhile, the economic impact of shutting down the town was already weighing on the minds of Los Alamos officials and business owners. Tucker said that unlike last time a fire forced the town's evacuation, none of the utilities have been shut off and no structures have been lost.
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