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…

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.