Italian law enforcement officials announced Friday they had arrested eight people in Switzerland who possessed $6 trillion of counterfeit U.S. Treasury bonds.  

The bonds were found in the compartments of three safety deposit boxes in Zurich, according to Bloomberg. The U.S. embassy in Italy examined the bonds and found the securities each had a nominal value of $1 billion. U.S. officials affirmed the bonds were fake.

Those bonds were moved in 2007 from Hong Kong to Zurich. Phone conversations intercepted by police found the individuals were planning on buying plutonium from Nigerian sources, Bloomberg reported.

This is not the first incident of bond fraud in the country. Italian police seized counterfeit Treasury bonds with a face value of $116 billion in August of 2009 and $134 billion in June of that year. Six people were caught in January of last year at a highway rest stop smuggling €20 billion ($26.3 billion) in U.S. treasury bonds.

The $6 trillion in counterfeit bonds seized is nearly 40 percent of the U.S. national debt, which currently is about $15.36 billion.