Authorities closed off a New Mexico atomic-material entombment complex after detecting abnormal radioactivity at the site, the Los Angeles Times reports.
Administrators barred employees from entering the subterranean storage area of the Waste Isolation Pilot Plant, paving the way for a probe into why detection equipment warned of unusual radiation in the area late on Friday night. No personnel were in the underground section at the time of the 11:30 p.m. alert.
"Officials at WIPP continue to monitor the situation," Energy Department spokeswoman Deb Gill said. "We are emphasizing there is no threat to human health and the environment."
The magnitude of any contaminant threat in the area was uncertain, as were any options for decontaminating affected portions of the site. Few details were available from plant personnel on possible sources of the contaminants.
The timing of the site's reopening was undecided, and a lengthy halt in operations could cause unwanted nuclear material to accumulate at numerous nuclear-arms sites across the United States, according to the Times. Twelve U.S. atomic-arms facilities together sent an average of more than two waste deliveries each day to the site, which handles transuranic waste containing plutonium, the newspaper said.
Edwin Lyman, a nuclear expert with the Union of Concerned Scientists, suggested the detected contaminants likely came from the exterior of a waste tank that had not undergone adequate cleaning.
He said a chemical reaction inside a storage tank might conceivably have enabled contaminants to escape, but regulations are in place for any such occurrences.
"It could be a mess," Lyman said. "If there is airborne contamination and it involves plutonium, they are going to need to decontaminate surfaces. If it is in the ventilation system, it could have spread to other areas."
More hazardous nuclear waste was once slated for storage at Yucca Mountain in Nevada, but President Obama has suspended work on that site.