One of the main nuclear weapons research laboratories in the US has been forced to close as fire fighters fight to quell a wildfire which threatens the facility.
Los Alamos was created during World War II as part of the Manhattan Project to build the atomic bomb and produced the weapons that were dropped on Hiroshima and Nagasaki.
Thousands of drums of plutonium-contaminated waste are stored at the facility and authorities have stepped monitoring of the air for radiation.
Officials have given assurances that dangerous materials are safely stored and capable of withstanding flames from the 240 square kilometer fire, which is as close as 15 metres from the grounds.
A small patch of land on the laboratory grounds caught fire on Monday before firefighters quickly put it out.
"We are throwing absolutely everything at this that we got," Democratic congressman Tom Udall of New Mexico said in Los Alamos.
The fire has forced the evacuation of the entire city of Los Alamos, population 11,000, cast giant plumes of smoke over the region and raised fears among nuclear watchdogs that it will reach as many as 30,000 drums of plutonium-contaminated waste.
"The concern is that these drums will get so hot that they'll burst. That would put this toxic material into the plume. It's a concern for everybody," said Joni Arends, executive director of the Concerned Citizens for Nuclear Safety, an anti-nuclear group.
A spokeswoman said the drums contain Cold War-era waste that the drums are designed to a safety standard that would withstand a wildland fire worse than this one.
Los Alamos employs about 15,000 people, covers more than 93 square kilometers, includes about 2,000 buildings at nearly four dozen sites and plays a vital role in the nation's nuclear program.
In the decades since, the lab has evolved into a major scientific and nuclear research facility. It stockpiles aging atomic materials, tests warheads, produces triggers for nuclear weapons and operates supercomputers and particle accelerators.
AP