The wildfire that surrounds the nuclear lab in Los Alamos, N.M., has grown to at least 61,000 acres amid mounting concerns about what might be in the smoke that's visible from space.
Such fear has prompted fire crews to set their own fires along the perimeter of the lab. So far, the strategy is working. The first air samples show lots of smoke, but no signs of elevated radiation.
"Those results show that what we see in this fire is exactly what we see in any fire across New Mexico," said Charles McMillan, the lab's director.
Environmental officials aren't taking any chances. The Environmental Protection Agency is bringing in dozens of air monitors all around the state, along with a special airplane that takes instant radiation samples. So far, officials have not been able to find anything amiss.
"Our facilities and nuclear material are protected and safe," McMillan told ABC News.
Some observers are worried not just about the barrels of nuclear waste stored at the lab, but also what's in the canyons that surround the sprawling complex. Nuclear tests were performed in the canyons dating back to the 1940s.
"The trees have grown up during that time frame and the soil could be contaminated," said Rita Bates of the New Mexico Environment Department. "If it gets heated and that stuff goes airborne, then we are concerned about that."
The canyons were a dumping ground for radioactive materials decades ago, but are now open to the public and are considered safe.
Still, one graduate student armed with a Geiger counter took to YouTube to show there was no shortage of metal or radioactivity.
Much of the area burned in the massive fire that blazed through the area in 2000, and no elevated levels of radiation were detected then.
The Los Alamos facility -- the birthplace of the atomic bomb -- was shrouded in secrecy long before it was surrounded by smoke after the Las Conchas fire began Sunday.
"It contains approximately 20,000 barrels of nuclear waste," former top security official Glen Walp said. "It's not contained within a concrete, brick-and-mortar-type building, but rather in a sort of fabric-type building that a fire could easily consume.
"Potential is high for a major calamity if the fire would reach these areas," he added.
The flames from the 108-square-mile fire reportedly have reached as close as 50 feet from the grounds. With a wildfire so close, lab officials, along with government officials such as New Mexico Gov. Susana Martinez, are trying to reassure the public of the plant's safety.
"I'm confident in saying that they are committed to making it safe," Martinez told ABC News.
Thousands Evacuated, Some Remain
After a mass evacuation, the city of Los Alamos remains a ghost town. Most of its 12,000 residents were evacuated Monday, with some leaving their sprinklers on to protect their homes.
Still, according to Police Chief Wayne Torpy, about 150 die-hard residents have stayed behind, unfazed by the danger presented by their nuclear neighbor.
"I know the laboratory is secure and they're ready for this kind of emergency situation," Stephanie Chavez, a resident of Los Alamos, told ABC News.
Firefighters have made progress in the past few days, and have said that the risk of the flames reaching radioactive material is slim. Still, they cautioned that winds Wednesday could change, as could their level of confidence.
"It's a lot better that it's down," said Doug Tucker, chief of the Los Alamos Fire Department. "But we can't relax. It's better, but we can't relax quite yet."
The fire began around 1 p.m. Sunday, according to a report by InciWeb, which provides the "incident information system" and compiles information from government agencies. The report indicated that Sunday's weather conditions included high temperatures, low humidity and high winds, all of which contributed to the inferno.