The shipping label said the mailed package contained replicas of Peruvian ceramics. An X-ray machine used by customs agents discovered it really held three skulls and a mummy more than 2,000 years old.
Authorities said Friday that the package was intercepted at Argentina's central post office, and an Argentine citizen who was waiting for the shipment has been detained as part of an investigation into illegal trading in ancient cultural artifacts.
Officials speculated the package would have been relayed to a museum or a private collector in Europe, where such old bones are in demand because of the blankets and other woven material that surround ancient South American mummies.
A preliminary evaluation by Argentina's national archaeology institute determined that the bones are from the pre-Inca Paracas culture on Peru's coast, and date from between the 7th and 3rd centuries B.C., officials said.
Authorities said the artifacts were mailed from La Paz, Bolivia, with the false contents declaration.
Last year, Bolivian police foiled a similar mummy mailing enterprise and detained a woman who tried to send a Peruvian mummy to France.