Twenty-five cultural artefacts that were smuggled into the United States have been returned to Italy.

The priceless collection contains fragments of frescoes from Pompeii, Greek and Etruscan vases, and rare 17th-century books. 

They have all been surrendered following an international investigation into stolen treasures.

Some of the items were found at auction houses,  while others were located in museums, universities and private collectors. The items were bought in good faith after the sellers concealed their provenance.

Homeland Security Investigations unit of the US Customs Service placed some of the blame for the crime on the internet.

“The crime may be ancient, but the perpetrators are very modern,” they said in a statement.  “The use of the internet has provided these criminals the ability to acquire, transport, advertise and sell valuable cultural property swiftly, easily and stealthily, while making it easier to evade detection by law enforcement agencies.”

They believe that this is just a fraction of the cultural objects that are currently on the market illegally. The agency said that the US have returned more than 7,600 objects to more than 30 countries and individuals since 2007.

Interpol estimates that the illicit trading in cultural heritage makes in excess of $9 billion (£5.85bn) in profits each year.

No criminal charges have been filed regarding the returned artefacts. This is either because of the complexity of their provenance, or because the statute of limitations has expired.

John Phillips, the American ambassador to Italy, said: “Italy is blessed with a rich cultural legacy and therefore cursed to suffer the pillaging of important cultural artefacts.”