Firefighters battling a wildfire near New Mexico's Los Alamos National Laboratory deliberately set part of the lab's perimeter ablaze, officials said.
Firefighters said they believe a blackened ring of burned vegetation will protect the nuclear lab and the radioactive material it houses by denying the wildfire fuel, ABC News reported Thursday.
"We are in the best shape we've been in since thing started," Los Alamos County Fire Chief Doug told ABC News.
The fire, which has burned more than 90,000 acres, prompted a mass evacuation, leaving the city of Los Alamos a virtual ghost town.
The laboratory was to remain closed at least through Friday, lab officials said.
A plane equipped with radiation monitors flew over the lab Wednesday -- a move lab authorities said was a precaution.
Meanwhile, New Mexico Gov. Susana Martinez examined some of the first air-quality tests from the Los Alamos area. Although the sampled indicated a lot of smoke, officials said no radiation had been released.
"Those results show that what we see in this fire is exactly what we see in any fire across New Mexico," LANL Director Charles McMillan said.
To ensure accuracy of the sampling, the U.S. Environmental Protection Agency delivered dozens of air monitors across New Mexico, along with a special airplane that takes instant radiation samples. So far, officials report nothing is abnormal.
However, environmental officials told ABC News they were concerned about vegetation on the lab's grounds and in surrounding canyons because of nuclear tests performed in the canyons dating back to the 1940s.
"The trees have grown up during that time frame, and the soil can also be contaminated. If they get heated and that stuff goes airborne, then we are concerned," Rita Bates of the New Mexico Environment Department said.