Authorities in Switzerland have confiscated $6 trillion (SFr5.5 trillion) in counterfeit US bonds at the request of Italian prosecutors.
In Italy on Friday, eight people were arrested across the country and placed under investigation for fraud and other crimes.
The bonds, carrying the false date of issue of 1934, had been transported in 2007 from Hong Kong to Zurich, where they were transferred to a Swiss trust, according to prosecutors in the southern Italian city of Potenza.
Authorities said United States officials had confirmed the bonds were counterfeit.
Prosecutors said the fraud had not been completed, but that it appeared that the suspects intended to try to sell the fake bonds to a developing nation, directly or through an intermediary bank.
Recently, Italian police carrying out a routine search at a motorway service station found a briefcase containing $20 billion in fake bonds.