(CNN) -- The federal government evacuated some workers Tuesday at the Hanford Site, a former nuclear weapons production site in Washington state, after soil collapsed over a tunnel containing contaminated material.
"There are concerns about subsidence in the soil covering railroad tunnels near a former chemical processing facility. The tunnels contain contaminated materials," the US Department of Energy said in a statement. Workers in other areas of the Hanford Site have been told to stay inside.
The Hanford Emergency Information website says soil collapsed over a tunnel next to the Plutonium Uranium Extraction Facility, but there is no evidence of contamination at this point. Responders are on scene to inspect the area. The tunnels are described as being hundreds of feet long and the collapse was spotted by workers doing routine surveillance.
"Secretary Perry has been briefed on the incident at DOE's Hanford site. Everyone has been accounted for and there is no initial indication of any worker exposure or an airborne radiological release. The Department will continue to monitor this closely and provide information and updates as they become available," said a statement from the Department of Energy Tuesday.
Since 1989, the government has been in the process of cleaning up the site.
"Hanford made more than 20 million pieces of uranium metal fuel for nine nuclear reactors along the Columbia River. Five huge plants in the center of the Hanford Site processed 110,000 tons of fuel from the reactors, discharging an estimated 450 billion gallons of liquids to soil disposal sites and 53 million gallons of radioactive waste to 177 large underground tanks," the US Department of Energy's Office of Environmental Management said on its website.
Hanford became a focal point of US nuclear efforts beginning in 1943, when aspects of the Manhattan Project were moved there. Thousands of workers moved into the site where plutonium was produced for use in atomic bombs. Material from the Hanford Site was used in the bomb dropped on Nagasaki, Japan, during the final days of World War II.
The site -- about half the size of Rhode Island, in an area centered roughly 75 miles east of Yakima -- continued to buzz during the Cold War, with more plutonium production, as well as the construction of several nuclear reactors.
The last reactor shut down in 1987, shortly before the mammoth cleanup effort began.
CNN's Ross Levitt contributed to this report
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