Thousands of residents calmly fled Monday from the mesa-top town that's home to the Los Alamos nuclear laboratory, ahead of an approaching wildfire that sent up towering plumes of smoke, rained down ash and sparked a spot fire on lab property where scientists 50 years ago conducted underground tests of radioactive explosives.
Los Alamos National Laboratory officials said that the spot fire was soon contained and no contamination was released. They also assured that radioactive materials stored in various spots elsewhere in the sprawling lab were safe from flames.
The wildfire, which began Sunday, had destroyed 30 structures south and west of Los Alamos by early Monday and forced the closure of the lab while stirring memories of a devastating blaze in May 2000 that destroyed hundreds of homes and buildings.
"The hair on the back of your neck goes up," Los Alamos County fire chief Doug Tucker said of first seeing the fire in the Santa Fe National Forest on Sunday. "I saw that plume and I thought, 'Oh my God, here we go again.' "
Tucker said the current blaze -- which grew Monday to roughly 50,000 acres, or 78 square miles -- was the most active fire he had seen in his career. By midafternoon, it had jumped a highway and burned an acre of land on the outskirts of the lab's 36-square-mile complex.
The fire scorched about an acre in the area that is known as Tech Area 49, which was used in the early 1960s for a series of underground tests with high explosives and radioactive materials. Lab officials said the fire was safely extinguished.
Lab spokesman Kevin Roark said environmental specialists from the lab were mobilized and monitoring air quality on Monday, but that the main concern was smoke.
The anti-nuclear watchdog group Concerned Citizens for Nuclear Safety, however, said the fire appeared to be about 3 1/2 miles from a dumpsite where as many as 30,000 55-gallon drums of plutonium-contaminated waste were stored in fabric tents above ground. The group said the drums were awaiting transport to a low-level radiation dump site in southern New Mexico.
Lab spokesman Steve Sandoval declined to confirm that there were any such drums currently on the property.
Traffic on Trinity Drive, one of the main roads out of Los Alamos, was bumper-to-bumper Monday afternoon as residents followed orders to leave. Authorities said about 2,500 of the town's roughly 12,000 residents left under an earlier voluntary evacuation.
Meanwhile, there was concern in the Midwest about a flood's effect on more nuclear facilities.
The nation's top nuclear power regulator said Monday that both of Nebraska's nuclear power plants have remained safe as they battle floodwaters from the bloated Missouri River.
Nuclear Regulatory Commission Chairman Gregory Jaczko visited both Fort Calhoun and Cooper nuclear power plants in eastern Nebraska this week to see how the utilities that run them are coping with the flooding. Both plants sit on the river.
The Omaha Public Power District's Fort Calhoun is the subject of more public concern because the floodwaters are closer to that plant. Nebraska Public Power District's Cooper plant is more elevated.
Jaczko's visit to Fort Calhoun Monday came one day after an 8-foot-tall, water-filled temporary berm protecting the plant collapsed early Sunday.
Vendor workers were at the plant Monday to determine whether the 2,000 foot berm can be repaired.
"We don't believe the plant is posing an immediate threat to the health and safety of the public," Jaczko said.