An internal investigation at an Overton plant found that staff had falsified documents for customers.
The worlds largest banknote printer, De La Rue, passed the findings from the investigation to the Serious Fraud Office.
The company, which prints notes for the Bank of England and 150 other countries halted production on July 21 after issues with paper quality.
De La Rue CEO James Hussey stood down from his role on August 12.
Since ceasing production, the firm launched an internal inquiry into the failure where the revelations came to light.
De La Rue chairman Nicholas Brookes told reporters the behaviour of those concerned was unacceptable and not in line with De La Rue's standards.
He said that the board had taken the appropriate disciplinary measures and action is being taken.
The firm has warned that it could lose at least £35 million in profits due to a loss of sales volume.
