FLAGSTAFF, Ariz. (CBS Local) — If you visited the Grand Canyon’s museum collections building in the last two decades, you may have been exposed to unsafe levels of uranium.

The park’s health and safety manager says the exposure came from uranium rocks stored in three five-gallon buckets between 2000 and June 18, 2018.

The uranium ore in question was found stored next to a taxidermy exhibit at the museum, the Arizona Republic reported. The National Park Service removed the buckets last June and dumped the contents into a defunct uranium mine.

The containers could have exposed adults to 400 times the health limit, and for children, up to 4,000 times what is considered safe.

The Arizona Republic cited the Grand Canyon’s safety director, Elston “Swede” Stephenson, in saying the park failed to warn workers or the public of the potential harm that existed for years.

“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 Feb. 4, according to the newspaper. “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 claimed he asked National Park executives to publicize the risks, but was ignored.

A spokesperson for the Grand Canyon told the newspaper a recent test revealed only background radiation, which is normal, and said there is no danger to the public.

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