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Workers at the Hanford Nuclear Reservation on Thursday finished filling a hole that was left after a tunnel that housed hot, radioactive material collapsed on Tuesday.

Fifty-three dump trucks full of soil filled the 400-square foot hole over the tunnel containing radioactive waste stored on the former plutonium production site.

The Energy Department says no one was injured in Tuesday's incident and no radioactive material escaped.

Most Hanford employees are reporting back to work Thursday except those who work near the Plutonium Uranium Extraction (PUREX) tunnel. That area remains restricted.

"Our next step is to identify and implement longer-term measures to further reduce risks," Energy Secretary Rick Perry said in a statement. "This week's incident is a reminder that the men and women who work for the Department of Energy do incredible work, but that work does not come without risk. Thankfully, the system worked as it should and all are safe. As Secretary, the safety of our workforce, the communities and tribal nations that surround our sites, and the environment is my highest priority."

Washington Gov. Jay Inslee on Wednesday said the state plans to issue an order requiring the federal government to determine the cause of a tunnel collapse at the Hanford Nuclear Reservation in Washington state.

The enforcement action announced Wednesday also requires the Energy Department to assess if there's an immediate risk of failures in any other tunnels and take actions to safely store waste in the tunnels until a decision is made about how to permanently handle the material.

The federal agency was expected to take those actions without prodding, but the state made the move in its role as the regulator of a massive, ongoing cleanup of the site.

Inslee says the state has an obligation to protect its residents and that the action is appropriate and necessary.

The state and federal government signed an agreement in 1989 setting deadlines for Hanford cleanup activities. The state monitors activities at Hanford as part of that deal.