Police said they detained two suspects with the printing presses still running at the 6 August raid on premises in the Newtonabbey area of County Antrim.
Members of the Serious Crime Squad described it as a major counterfeiting operation with the ability to produce sizeable quantities of currency, and said they were conducting more searches on premises that they believed could be connected to the operation.
Two men were arrested in connection with the operation and are helping police with their enquiries.
Euros, sterling and Irish punts were among the currencies being printed at the house.
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