CHICAGO, Illinois — Six human skulls that were bound for an address in Iowa were intercepted by Customs agents in Chicago last month. It happened on March 29th at O’Hare Airport, according to a news release from US Customs and Border Protection.

Customs agents were x-raying a shipment that was heading to Iowa from the Netherlands when they spotted “anomalies”. Further inspection revealed three packages, each containing two human skulls. The six skulls were confiscated and turned over to the CDC to be disposed of.

The concern isn’t the macabre nature of the shipment, but the potential biohazards for the CBP. “Our nation’s food supply is constantly at risk from pests and disease not known to occur in the U.S.,” said LaFonda D. Sutton-Burke with the CBP in Chicago, “These significant interceptions … exemplify CBP’s continued commitment to safeguarding American agriculture.”

This wasn’t the only big biohazard bust for CBP in Chicago last month. On March 8th a canine detected something suspicious in three packages being shipped from Poland. Inside were live moss bathmats that hadn’t been declared through customs. The mats were destroyed using steam sterilization. The CBP says the mats could have introduced non-native plant diseases or insects into the US ecosystem.

Customs and Border Patrol says you should review their information center or contact them online or by phone at 1-877-227-5511 with any questions about an international shipment.