Two directors from a Zeeland fish and mussel wholesale firm have been arrested for multi-year fraud, public broadcaster Nos said on Thursday.

The men are said to have helped Belgian restaurant owners and market stall holders defraud the tax office by writing thousands of fake bills so fish and mussels could be sold on the black market.

Investigators have declined to say how much money is involved because the investigation is still ongoing. More arrests in the Netherlands may follow.