They were accused of buying and reselling stolen goods. Police in Italy, Hungary and Slovenia also searched about 60 homes and businesses.
Police picked up one of the group's leaders, who was not named, at the Italy-Slovenia border carrying 200,000 euros in cash obtained by selling stolen gold, finance police official Filippo Ivan Bixio told Reuters.
The group, which was based in the northern industrial city of Turin, bought stolen objects from a network of contacts, paying them in cash at a discount of about 30 percent compared with market prices, Bixio said.
A company set up in Budapest issued fake purchase receipts without ever taking possession of the gold. It then sold the precious metal to the countries' largest jewellers at market prices.
The Italian companies paid the Hungarian company by bank transfer, so each week one of the group's leaders drove from Turin to Budapest to pick up 200,000 to 300,000 euros in cash to pay for more stolen gold.
"They paid their suppliers in cash," Bixio said. "Then they melted it down into small bars and sold it to Italy's three or four top buyers, who thought they were buying gold from Hungary, but in reality it was Italian."
During the investigation, police documented the purchase of 750 kg (1,700 lb) and the laundering of some 25 million euros in stolen gold, police said.
Eurojust, the European Union's judicial cooperation agency, helped Italian authorities coordinate the operation with their counterparts in Hungary and Slovenia.
(Reporting by Steve Scherer; Editing by Alison Williams)
