A mysterious container warning "caution radioactive material" was found on a Wisconsin beach on Wednesday morning.

The U.S. Coast Guard reported that the responding agencies determined that the container, found on a beach near the mouth of the Poplar River, didn't contain radioactive materials.

A person walking on the beach saw the container, which was about the size of a deck of cards, and immediately called local emergency services, according to the Coast Guard.

Initial responders from the Coast Guard and Superior Fire Department determined that the container wasn't emitting any radioactivity. In a follow-up investigation, authorities ensured there was no radiation source from the surrounding area and that the object was not a hazard to the public. The Wisconsin Department of Health Services removed the container for proper disposal, according to the Coast Guard.

The agencies weren't able to determine what the container was or where it came from, according to the Superior Fire Department.

Thanking the person who found the container, the responding agencies reminded the public to report anything suspicious or unusual to their local emergency services.

"Our swift mobilization of local, state and federal resources for this response reinforced our unified effort to address potential threats to public safety, especially on the eve of the Tall Ships Duluth festival, a historically well-attended public event," Commander Erin Williams of the Coast Guard Marine Safety Unit Duluth said in a statement.