U.S. Energy Secretary Rick Perry says a hole that developed in the top of a nuclear waste storage tunnel in Washington state has been filled.
Perry announced Thursday morning that the 400-square foot (37 square meter) hole was filled swiftly and safely. He says the next step is to reduce risks at the aging tunnel.
The hole was discovered Tuesday morning on top of a nuclear waste storage tunnel on the Hanford Nuclear Reservation. Workers started filling the hole Wednesday.
The cause of the partial collapse of the tunnel, which was built in 1956, has not been determined.
The Energy Department has said no one was injured in the incident and no radiation was released to the environment.
Hanford for decades made plutonium for nuclear weapons.