A shipment containing 10th century artifacts was intercepted by U.S. Customs and Border Protection officers in Louisville, the agency said.
The items were on their way from Mexico to a residence in Sumter, South Carolina, when they were seized July 24, according to a news release.
An expert determined that the pieces in the collection — a skull and 12 chopping tools — dated back to the Post-classical and Aztec eras, from 1100-1532.
"I'm extremely proud that our officers were able to stop priceless artifacts from being lost forever," LaFonda Sutton-Burke, the agency's field operations director in its Chicago office, said in the statement.
"Customs and Border Protection will continue to use our border authority to identify and rescue precious antiquities being smuggled by those who profit on the theft of historical and cultural property and return them to their rightful owners."
Most countries have laws that protect cultural property, such as artifacts, that include export controls and national ownership. The agency says importers must have permits and receipts when bringing such items into the U.S.
The Department of Homeland Security enforces cultural property import restrictions set in agreements between the U.S. and 20 countries, and through emergency import restrictions with three other countries.
Restricting the importation of certain archeological material reduces the motivation for looting at historic sites, according to Customs and Border Protection.
The agency says it has seized cultural property 21 times since the start of the 2020 fiscal year. The items valued more than $18 million.