A 40ft trailer set up as a mobile fuel laundry with oil laundering apparatus was seized on Thursday near Carrickmacross.
A lorry with a 40ft tanker which contained suspected waste from fuel laundering was also seized.
Gardai from the Carrickmacross assisted by the Armed Support Unit in Cavan were involved in a Cross Border Joint Action Task Force Operation.
As part of this operation they assisted Revenue Officers in the execution of a search warrant at a yard near Carrickmacross.
Local gardai said those involved in the laundering of fuel are posing a risk to legitimate business and the waste product is harmful to the environment.
An Garda Siochana say they are committed to working with our partners in this jurisdiction and in Northern Ireland in investigating all types of cross border crime.