Italian police said Thursday they have recovered about 300 ancient artifacts and thousands of fragments believed to have been illegally excavated in central Italy.

Six people were under investigation on possible charges including trafficking of antiquities, but nobody has been arrested, Rome Carabinieri police said.

The items recovered include vases, jars and cups. Among the most precious objects was a 29-centimetre Greek vase dating to 600-580 B.C. and featuring black figures. Some of the items were sold at the Porta Portese flea market, held every Sunday in Rome.

Col. Ferdinando Musella, an official with Italian anti-art theft police, said that tombraiders often break vases and amphorae so that they can sell single pieces and then ask for a higher price for the missing piece that would complete the artifact.

Italy is aggressively combating the pillage of its archaeological and artistic treasures. Its campaign also includes seeking the return of several antiquities it claims were obtained by museums illegally.