CHICAGO—A shipment of 18 human heads held up by customs officials at O'Hare International Airport was bound for a cremation service in the Chicago area after its use in medical research abroad.

A spokeswoman for the Cook County Medical Examiner's Office, Mary Paleologos (PEHL'-ee-oh-loh-gohs), said Tuesday that the heads were originally sent from Illinois to Italy for medical research and were returned to the area for disposal as part of the agreement.

She says a paperwork problem held up the shipment, which arrived at O'Hare in mid-December.

The containers were being stored at the Cook County morgue while authorities investigated the matter.

Paleologos says the heads will be turned over for cremation.