Updated at 5:10 p.m. ETThe Department of Energy has declared an emergency at a nuclear-contaminated site in Washington state, after soil caved in over a portion of a tunnel containing rail cars contaminated with nuclear waste."All personnel in the immediate are have been accounted for — they are safe — and there is no evidence of a radiological release," Destry Henderson, spokesperson for the Hanford site's emergency operations center, said in a brief statement on Facebook.Some employees were evacuated and others were told to move indoors as a "precaution," officials say. Anna King of the Northwest News Network, a public radio station collaboration, reports that approximately 3,000 other workers in the area were originally taking cover indoors. Non-essential employees and those farther from the tunnel have since been sent home.There are no reports of injuries.The Hanford Site, about 150 miles southeast of Seattle, is a former nuclear production complex and home to a long-running, challenging and sometimes troubled cleanup operation.It's generally regarded as the most contaminated nuclear site in America. The Department of Energy says it's the most challenging of the government's nuclear cleanup projects, with millions of tons and hundreds of billions of gallons of nuclear waste.The Department of Energy says a 20-foot-by-20-foot section of soil caved in where two underground tunnels meet next to the Plutonium Uranium Extraction Facility, known as the PUREX plant.The tunnels in question were storing rail cars that once carried radioactive nuclear fuel from reactors to production facilities, back when the site was still used to manufacture nuclear weapons. Each tunnel is hundreds of feet long, the Hanford Site says; a 20-foot section appears to have collapsed."There is no indication of a release of contamination at this point," the Department of Energy says. Workers are continuing to evaluate the situation, with the help of a remote-controlled device.The site of the collapse had been previously identified as a potential hazard, the Northwest News Network writes: