The U.S. Energy Department on Monday said testing had revealed trace levels of contamination in four additional workers at a nuclear waste site in New Mexico.
The announcement brings to 21 the total number of Waste Isolation Pilot Plant, or "WIPP," personnel who were exposed to small amounts of radiation following a February leak of some radioactive elements from the subterranean nuclear-materials dump, the Associated Pressreports.
The department intended to dispatch a team of eight specialists on Tuesday into the underground portion of the nuclear facility to start establishing outposts that would enable a probe into exactly what led to the leak.
The WIPP facility has not accepted any new atomic waste since the discovery of the radiation leak. This has caused some U.S. nuclear-weapons sites to turn to temporary options for storing their waste.