The toxic heavy metal beryllium has mysteriously cropped up in a U.S. Department of Energy complex in North Las Vegas, and investigators believe it may have come from a 1965 nuclear reactor explosion some 85 miles away.

In March of 2002, a contract worker at the complex was diagnosed with chronic beryllium disease, which can damage lung tissue, causing shortness of breath and, in extreme cases, disability or death. “(We) were all alarmed and didn’t know what to do,” says Dr. Louis Pepper, who tests former Nevada Test Site workers for beryllium exposure. While the contamination was kept secret until this fall, by August of 2002, the Energy Department had quietly relocated all 650 employees and closed down the entire complex.

One likely source of the contamination is the 38-year-old “Kiwi” experiment at the Nevada Test Site, which tested the possibility of using nuclear reactors to power spaceships. As part of the experiment, scientists deliberately destroyed a modified nuclear reactor. Energy Department workers did cleanup work in the 1960s, and then again between 1996 and 1997. Investigators believe that workers may have tracked beryllium back to the Las Vegas office during the second cleanup.

“We’re seeing it in the loading dock area of the building, in crevices and on floors — ultimately, it’s in the carpet,” says Darwin Morgan, National Nuclear Security Administration spokesman. The Energy Department is now considering whether to clean up the 140,000-square-foot complex or shut it down permanently. The agency estimates that $2 million and six months will be required to determine the exact cause of contamination.