For nearly two decades at the Grand Canyon, tourists, employees, and children on tours passed by three paint buckets stored in the National Park's museum collection building, unaware that they were being exposed to radiation.

Federal officials learned last year that three five-gallon buckets stored in the Grand Canyon’s museum building were literally overflowing with highly-radioactive uranium ore. The buckets were moved to the museum building when it opened in 2000 and were so full of the ore one literally wouldn’t close.

As AZCentral.com reports, in a rogue email sent to all Park Service employees on Feb. 4, Elston "Swede" Stephenson - the safety, health and wellness manager - described the alleged cover-up as "a top management failure" and warned of possible health consequences.

"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."

Stephenson says he tried to convince Parks executives to warn the public that anyone visiting the site after 2000 could have been exposed to radiation he calculated at levels potentially over 4,000 times the Nuclear Regulatory Commission’s “safe” level for children and 400 times the level for adults, but was “stonewalled” by management. He believes the Park Service violated the law by not informing the public of the danger.

“Respectfully, it was not only immoral not to let Our People know, but I could not longer risk my (health and safety) certification by letting this go any longer,”

Stephenson released a 45-page report detailing the allegations.

As RT reports, the radioactive hoard was discovered by a teenager with a Geiger counter during a museum tour and promptly swept under the rug, Stephenson says, adding that technicians dumped the ore into an old mine near Grand Canyon Village, concealing their meter readings from him the entire time they were cleaning up the radioactive mess.

Alarmed at their unprofessional behavior, he called in the Occupational Health and Safety Administration, who found only the empty drums – which had been “inexplicably returned to the building” and still gave off faint radiation readings.

Emily Davis, a public affairs specialist at the Grand Canyon, said the Park Service is coordinating an investigation with the Occupational Safety and Health Administration and the Arizona Department of Health Services. AZCentral reports that Davis stressed that a recent review of the building in question uncovered only background radiation, which is natural in the area and is safe.

"There is no current risk to the park employees or public," Davis said. "The building is open. ... The information I have is that the rocks were removed, and there's no danger."

Davis declined to address Stephenson's assertion that thousands of people may have been exposed to dangerous levels of radiation, or his allegation that the Park Service violated the law by not issuing a public warning.