U.S. Customs and Border Protection officers in Philadelphia intercepted a shipment of the club drug ketamine that they found hidden inside of metal cocktail sticks.

The international air parcel from Italy was headed to an address in Worcester, Mass. An X-ray examination detected anomalies after the package arrived here on June 10, CBP officials announced on Monday.

Ketamine is an anesthetic, used in the 1960s to ease pain among wounded soldiers in Vietnam, and today employed by doctors and veterinarians. It can make it hard for people to speak or move, and is sometimes used during sexual assaults, according to WebMD.

When CBP inspected the box, officers found 36 metal tubes that each contained a white substance. They used a handheld analysis tool and identified the contents as ketamine, known on the street as Special K, officials said.

The shipment was seized and the investigation is continuing.