Hundreds of workers at a nuclear site in the western U.S. state of Washington were ordered to take cover Tuesday after part of an underground tunnel containing rail cars full of radioactive waste collapsed.
Officials detected no release of radiation at the Hanford Nuclear Reservation and no workers were injured, said Randy Bradbury, a spokesman for the Washington state Department of Ecology.
The cause of the collapse was not immediately known. No workers were inside the tunnel when it collapsed, causing soil on the surface above to sink up to 1.2 meters over 37.1 square meters area, officials said.
"All employees have been accounted for; there were no injuries and there is no indication of a spread of radiological contamination," said Destry Henderson, a spokesman for the Hanford Emergency Center.
The Hanford nuclear site was used to produce plutonium for the bomb that brought an end to World War II. Its last reactor closed down in 1987 but millions of liters of leftover waste are contained in tanks at the site.
The collapse was discovered during a routine inspection and occurred during a massive cleanup that has been under way since the 1980s and costs more than $2 billion a year. The work is expected to take until 2060 and cost more than $100 billion.
The Hanford Site suffered a leak in a massive nuclear waste storage tank in 2016 that was described as "catastrophic" by a former employee.
The U.S. Department of Energy downplayed the incident at the time saying the leak had been "anticipated" amid ongoing efforts to empty the tank.
