Three paint buckets filled with uranium sat in the Grand Canyon Museum Collection building for nearly two decades while tourists were unaware they were being exposed to radiation, a safety manager at the National Park has claimed.

The containers were removed from the site last year, but not brought to the public’s attention until this month, after Elston Stephenson, the park’s safety, health, and wellness manager, alerted his colleagues via email that nothing was done to warn employees or the public.

“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’s email read.

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Stephenson said the buckets were placed in an area where tours averaged 30 minutes and close exposure could have exposed adults to 400 times the health limit, and children 4,000 times.

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Emily Davis, a public affairs specialist at the Grand Canyon, said the Park Service has launched an investigation with the Occupational Safety and Health Administration and the Arizona Department of Health Services, the Arizona Republic reported. Davis said the building remains open.

"The information I have is that the rocks were removed, and there's no danger," Davis said.