Ancient artifacts worth an estimated €900,000 ($1 million) were seized by police in the central Lazio region of Italy on Friday. 

The antiquities, which reportedly date back to the 4th century BC and the 2nd century AD, were recovered by the Cultural Heritage and Anti-Counterfeiting department of the Carabinieri, the Italian police service. The seizure was reported in a notice on the Carabinieri’s website from ANSA, the country’s leading wire service.

The seizure was the result of a two-part operation: Police tracked the financial activity of two Roman businessmen who allegedly used large sums of money to buy artwork. According to police, one of the businessmen even set up a small private museum featuring dozens of objects of historical and artistic interest, including some ceramics and two coroplastic (ancient terracotta) heads: a bull and a horse, which likely belong to a larger sculptural grouping. He did this without informing the relevant offices of the Ministry of Cultural Heritage and Activities and Tourism (Mibact).

The second part of the operation involved monitoring online activity, particularly a Facebook profile which police say was used to sell a fragment of a Roman column made from tuff (porous rock formed by the consolidation of volcanic ash) dating back to the site of the ancient town of Ardea, 22 miles south of Rome. (Ardea was founded during the 8th century BC, and it is described in the Aeneid as being the capital inhabited by the legendary Rutuli tribe.)

The seizure of the artifacts is part of a recent trend in the marketplace, which has seen a surge in the sale of looted artifacts online. According to a Wall Street Journal investigation, 80 percent antiquities available online at any given moment have no recorded provenance—which means they are probably looted or fake. Two volatile factors are driving the spike: Unprecedented looting by ISIS across the Middle East has brought an avalanche of illicit objects into the marketplace. And novice collectors now have nearly unfettered access to un-vetted material as a result of the rapid growth of online outlets like Facebook, WhatsApp, eBay, and Amazon.

Artnet News has reached out to the Italian Carabinieri for more information about the antiquities seized in Lazio. This story will be updated as we learn more.