15,000 litres of laundered fuel was seized by Revenue officers in Wicklow.
The seizure, which was made today, included 10,000 litres in an oil tanker and 5,000 litres in a tank on a premises in Arklow, Co Wicklow.
The oil tanker transporting the fuel was also seized.
A new fuel marker enables Revenue to test samples of road diesel from distributors, forecourts and transport companies to identify the lower-taxed marked diesel intended for off-road use only, and take appropriate enforcement action where the marker is detected.
Investigations are ongoing in the case, with a view to criminal prosecution.