DENVER (AP) — A U.S. official harshly criticized a Colorado health officer who questioned the safety of a former nuclear weapons plant and said he did not trust the federal government's assurances that the site was thoroughly cleaned up before being converted into a wildlife refuge.

The dispute is part of a decadeslong battle over the operation and cleanup of the Rocky Flats facility outside Denver, which made plutonium triggers for nuclear weapons for decades. Part of the site is now a wildlife refuge, and the government plans to open hiking trails and visitor facilities there this year.

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