U.S. Customs and Border Protection officers discovered several packages containing human skulls last month after the packages were screened at an international mail facility, bound for Iowa, officials said.

The skulls were discovered at O’Hare International Airport's International Mail Facility in Chicago, after CBP Agriculture Specialists determined that the boxes "showed anomalies," prompting additional search protocols.

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"Our nation's food supply is constantly at risk from pests and diseases not known to occur in the U.S. These significant interceptions by our CBPAS at the IMF at O’Hare exemplify CBP's continued commitment to safeguarding American agriculture," said Chicago Field Office Operations Director LaFonda D. Sutton-Burke.

U.S. Customs and Border Protection Agriculture Specialists (CBPAS) at the International Mail Facility (IMF) at O’Hare International Airport found human skulls among 1,667 prohibited items seized in transport.

U.S. Customs and Border Protection Agriculture Specialists (CBPAS) at the International Mail Facility (IMF) at O’Hare International Airport found human skulls among 1,667 prohibited items seized in transport. (U.S. Customs and Border Protection)

The officers x-rayed the three boxes and found two human skulls in one box — and two skulls in both other boxes — covered with protective packaging often intended for shipping fragile items, the CBP said.

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The unusual packages came into the U.S. from the Netherlands and were then transported to the Centers for Disease Control and Prevention for additional screenings, officials said.

A U.S. Customs and Border Protection agent.

A U.S. Customs and Border Protection agent. (U.S. Customs and Border Protection)

Other strange packages intercepted by CBP officers included three individual Live Pole Moss Bathmats that did not have proper permits to allow for travel, officials said.

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In total, the CBPAS officers seized 1,667 agriculture shipments containing prohibited items, according to the report.