SOFIA, Bulgaria (AP) — Police seized high-quality forged banknotes produced at a printing office at a university in Bulgaria's capital, authorities said Tuesday.

In a joint operation with the U.S. Secret Service, Bulgarian police detained two people and seized a printing machine and equipment for printing money, along with large amounts of counterfeit U.S. dollar and euro notes.

“The value of the seized currency is impressive. The material evidence speaks of serious criminal activity,” Sofia police chief Georgi Hadzhiev said Tuesday.

The amount of counterfeit money seized is $4 million and 3.6 million euros, according to the prosecutor’s office.

Police believe that the two suspects are part of a larger criminal enterprise, dealing in the trafficking of counterfeit dollars to Ukraine, and of euros to Western Europe.