Officials at Chicago's O'Hare International Airport revealed on Tuesday that they are holding a rather ghastly shipment of 18 human heads that arrived at the airport from Rome, Italy, allegedly on its way to a research facility.

"We are involved because they can't store them any longer," Tony Brucci, chief of investigations at the medical examiner's office shared with ABC News. "We'll be examining the heads in the autopsy room today, but there is no foul play suspected in the collection of the heads."

The heads were still covered in skin, ABC revealed, although it was not immediately clear in what kind of containers they were held. The research facility in Chicago that they were shipped to is apparently under investigation, the Chicago Tribune revealed.

The remains were shipped as cargo on a Lufthansa Airlines flight from Rome, and arrived in Chicago late last month – but a paperwork problem prevented them from delivered to their final destination. The research facility that is being investigated was not named.

"They were all properly preserved and tagged for the purpose of anatomical study. The paperwork just isn't properly done," Brucci added. The heads were first found when the containers containing them went under an X-ray scan.

"There's no issue with the transportation of body parts for medical purposes," Brian Bell, a spokesman with the U.S. Department of Homeland Security, explained. "There's nothing against the law that says you cannot ship them, provided you have the right documentation." What kind of research the heads were supposed to be used for, however, was not explained.

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Bell added that such shipments, although unusual, are not without precedent, and human body parts are transported through various ports in the country.

"People ship body parts to universities and hospitals all the time, we just don't usually hear much about it," Brucci agreed.

The shipment of heads were transported to the Cook County Medical Examiner's office for inspection, where it currently remains.