For years, tourists visiting the Grand Canyon in Arizona have been exposed to radiation in the national park's museum, it has been revealed.

Federal officials discovered last year that three 5-gallon paint buckets stored in the museum were actually filled with uranium ore, USA Today reports.

The radioactive specimens were removed, but the park's safety manager alleged workers and the public were not warned that they may have been exposed to unsafe levels of radiation.

An email sent out to employees on February 4 by safety, health and wellness manager Elston "Swede" Stephenson described the incident as a "top management failure", warning of potential health consequences.

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"If you were in the Museum Collections Building (2C) between the year 2000 and June 18, 2018, you were 'exposed' to uranium by OSHA's definition," Stephenson wrote.

"The radiation readings, at first blush, exceeds [sic] the Nuclear Regulatory Commission's safe limits. … Identifying who was exposed, and your exposure level, gets tricky and is our next important task."

The museum building is located in the Grand Canyon Village in Arizona.

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Stephenson said he has repeatedly asked management to inform the public, but was stonewalled.

"They're in cover-up mode," he said. "I've been cut off from any kind of information."

According to Stephenson, the containers were stored next to a taxidermy exhibit, where children sometimes stopped on tours for 30 minutes or more. He said the uranium could have exposed children to 4000 times the health limit for radiation and adults to 400 times.

Eventually, he obtained a report from the Park Service's regional safety manager, that confirmed the area was "positive for radioactivity above background" and showed high levels near the taxidermy area.

However, Emily Davis, a public affairs specialist at the Grand Canyon, said that a recent review of the building found only background radiation, which is natural in the area and safe.

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"There is no current risk to the park employees or public," Davis told USA Today.

"The building is open. … The information I have is that the rocks were removed, and there's no danger."

She did not address Stephenson's allegations.

"We do take our public and employee safety and allegations seriously," she said.