The Trump administration is moving ahead with plans to allow public access to a wildlife refuge in Colorado that surrounds one of the country's most contaminated former nuclear sites.

The Fish and Wildlife Service (FWS) on Saturday plans to make more than 5,000 acres available to the public in Colorado's Rocky Flats National Wildlife Refuge, located 12 miles northwest of Denver.

Earlier Friday, that decision was briefly delayed by Interior Secretary Ryan Zinke Ryan Keith ZinkeTrump extends Florida offshore drilling pause, expands it to Georgia, South Carolina Conspicuous by their absence from the Republican Convention Trump flails as audience dwindles and ratings plummet MORE.

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"Secretary Zinke has heard concerns about the opening of the Rocky Flats National Wildlife Refuge and has decided to delay the opening to gather additional information. The Secretary has asked Deputy Secretary Bernhardt to look into this matter,” an Interior spokeswoman said in a statement to The Hill.

But an hour after Interior announced the delay, it said the plans would move forward.

"The Deputy Secretary has reviewed the refuge and determined it will open tomorrow as scheduled," the department said.

The refuge, designated by Congress in 2011, surrounds a restricted Superfund site that for decades was a manufacturing site for the plutonium used in nuclear bombs. Plutonium particles are known to cause cancer.

The Environmental Protection Agency (EPA) and the Colorado health department both said the park is safe for use following tests that found only “an extremely small” increased risk for cancer in the area.

However, local environmental groups sued in May over health concerns, arguing that not enough testing had been done. The judge rejected attempts to keep the refuge closed to the public until a final ruling, which is still pending.

Colorado Rep. Jared Polis Jared Schutz PolisMore than 1,000 gather at Colorado racetrack to protest governor's coronavirus orders Over 300 LGBT leaders endorse Biden for president : 'The most pro-equality ticket in US history' Colorado GOP lawmaker, Michelle Malkin sue governor over coronavirus orders MORE (D), who is running for governor, fiercely opposes opening the area to the public.

"I will always choose the safety of my constituents above all else, and I think it’s best to err on the side of caution," he said in a statement Friday. "Opening the Refuge should happen after testing is completed and everything is determined to be safe."

In a letter he sent to Zinke Thursday, Polis argued that the last round of testing for contamination had been completed more than a decade ago and didn't take into account a 2013 flood that changed the topography.

"I am following up on my constituents' request that the Department of Interior (DOI) complete further testing of air, water and soil at the Refuge site by March 2019, and that until further testing has been completed, the Refuge site remain unopen to the public," Polis wrote.

—Updated at 6:58 p.m.