Workers at the Hanford nuclear site in Washington have sealed a hole that developed in one of the facility's tunnels this week.

Energy Secretary Rick Perry Rick PerryOVERNIGHT ENERGY: Democrats push resolution to battle climate change, sluggish economy and racial injustice | Senators reach compromise on greenhouse gas amendment stalling energy bill | Trump courts Florida voters with offshore drilling moratorium OVERNIGHT ENERGY: Trump signs major conservation bill into law | Senate votes to confirm Energy's No. 2 official | Trump Jr. expresses opposition to Pebble Mine project Senate votes to confirm Energy's No. 2 official MORE, whose agency oversees the site, said that “the system worked as it should and all are safe” at Hanford, where a 400-square-foot collapse occurred on Tuesday at a tunnel filled with radioactive waste.

“This was accomplished swiftly and safely to help prevent any further complications,” Perry said in a statement Thursday. “Our next step is to identify and implement longer-term measures to further reduce risks."

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Washington Gov. Jay Inslee Jay Robert InsleeBarr asked prosecutors to explore charging Seattle mayor over protest zone: report Bottom line Oregon senator says Trump's blame on 'forest management' for wildfires is 'just a big and devastating lie' MORE (D) on Wednesday said his state would issue an order requiring the federal government to figure out what caused Tuesday’s tunnel collapse, which happened near Hanford’s uranium extraction plant.

I'm glad the #Hanford workers are safe and we've seen no contamination. We'll be working on an enforcement order over the next 24 hours. pic.twitter.com/SGKNUhdFkl — Governor Jay Inslee (@GovInslee) May 10, 2017

“I am extremely concerned about what happened yesterday, and how the Department of Energy can give us confidence that this will not happen again,” he said at a press conference.

“The efforts to provide a long-term storage of the sludge and liquid waste is a tremendous challenge and we’ve got to remain insistent that the federal government comply with its obligations to do that, and we will continue to do that.”

Inslee said the situation had “stabilized” by Wednesday and that officials would continue to monitor air quality at the site. White House spokeswoman Sarah Huckabee Sanders said Wednesday that there had been “no indication of worker exposure or an airborne radiological release.”

For decades between World War II and the end of the Cold War, Hanford produced some of the radioactive material necessary for the development of the United States' nuclear weapons.

Today, the facility houses 56 million gallons of chemical and nuclear waste, and the federal government is overseeing a clean-up effort there that could take decades.