A suspicious box containing 18 severed human heads, still covered in skin, was discovered yesterday at Chicago O'Hare International Airport.

U.S. Customs and Border Patrol officials made the grisly discovery and have declined to discuss in more detail the condition of the heads. Officials are currently investigating whether the foreign shipment contains are legitimate medical specimen.

Customs officials have now handed the human body parts to the Cook County Medical Examiner's office for further inspection.

"We are involved because they can't store them any longer," the chief of investigations at the medical examiner's office Tony Brucci told 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."

While officials at the U.S. Department of Homeland Security confirmed that the fleshy human heads were shipped from a place outside U.S. borders, but they declined to specify the exact location. Officials also declined to say where or to whom the heads were supposed to be sent to.

However, The Chicago Sun-Times reported that the heads were shipped from Rome, Italy, and were en route to a research facility near Chicago, but were stopped because there was an error in the paperwork.

"They were all properly preserved and tagged for the purpose of anatomical study," Brucci said. "The paperwork just isn't properly done."

Brian Bell, a spokesman for the Department of Homeland Security told Chicago Herald Sun that the heads appeared to be medical samples.

"There's no issue with the transportation of body parts for medical purposes, there's nothing against the law that says you cannot ship them, provided you have the right documentation," Bell told the Chicago Herald Sun.

"Everybody here is 'Oh my gosh, you got a box of heads' and everybody thinks that it's unheard of," he said.

"It is a potentially legitimate medical shipment. We've seen it at various ports in the nation," Bell added.

Local authorities said that while there appears to be no foul play in the shipment, they will be investigating the case further.

In 2010, a shipment of 60 human heads and parts of heads wrapped with duct tape and loaded into plastic containers was seized at an airport in Arkansas. Those heads were later discovered to be for medical training, but were stopped in transit because of improper packaging and mistakes in paperwork.