A portion of an underground tunnel containing rail cars full of radioactive waste collapsed Tuesday at the Hanford Nuclear Reservation, in Washington State.
Officials detected no release of radiation and no workers were injured, said Randy Bradbury, a spokesman for the WA state Department of Ecology.
No workers were inside the tunnel when it collapsed, causing soil on the surface above to sink two to four ft over a 400 sq. foot area, officials said.
The tunnels are 100s of feet long, with about 8 feet of soil covering them, the U.S. Department of Energy said.
The cause of the collapse was not immediately known.
Workers near the site of the collapse were evacuated and hundreds of others farther away were told to remain indoors for several hours, the agency said. Some of the workers at the site were sent home early along a safe access route.
"No action is currently required for residents of Benton and Franklin counties," the U.S. Energy Department said, referring to the nearly 300,000 residents near the site about 200 miles southeast of Seattle. "There is no indication of a release of contamination at this point."
U.S. Energy Secretary Rick Perry was briefed on the incident that Washington Gov. Jay Inslee called it a serious situation.
"Ensuring the safety of the workers and the community is the top priority," said Inslee.