Story highlights $6 trillion is more than twice Italy's national debt

The bonds were discovered as part of an investigation into a local mafia group

Arrest order was issued in the southern Italian city of Potenza

8 people arrested after $6 trillion in fake U.S. bonds found in Italy

Italian authorities on Friday arrested eight people in possession of an estimated $6 trillion in counterfeit U.S. Treasury bonds, according to Italian paramilitary police and an Italian news agency.

The discovery of the fake bonds -- made to look as if they were printed by the U.S. Federal Reserve in 1934 -- came about as part of an investigation into a local mafia association.

The arrest order for the alleged criminals was issued by a preliminary investigative judge in the southern Italian city of Potenza, police noted.

Italian authorities, working with their Swiss counterparts, learned about the counterfeit bonds by way of eavesdropping on wiretapped phones, police said.

The total of $6 trillion is more than twice the Italy's national debt.

The Italian news agency, ANSA, reported that the bonds were also discovered "alongside copies of the Treaty of Versailles rolled inside lead cylinders."

CNN can not independently verify that account.