Minnesota health officials said Tuesday they are investigating a rare case of anthrax inhalation linked to exposure to the dreaded bacteria in the natural environment.
The FBI briefly investigated the case because anthrax has been used in terror attacks. But the bureau determined there was "no evidence suggesting it was a criminal or terrorist act," the Minnesota Health Department said in a statement.
There was also no significant threat to the general public, officials said.
"All evidence points to this case of anthrax being caused by exposure to naturally occurring anthrax in the environment," said Minnesota state epidemiologist Ruth Lynfield.
"Anthrax is not spread from person to person, and it is extremely rare for humans to become sickened with anthrax, especially through inhalation."
Hooved animals are regularly infected by the anthrax bacteria in many parts of the United States.
People can become sickened by anthrax if they handle infected animal carcasses, ingest contaminated soil or meat from infected animals, or handle contaminated wool or hides from infected animals.
The affected individual was hospitalized after traveling through western states -- including North Dakota, Montana, Wyoming and South Dakota -- and coming into contact with soil and animal remains.