A gang involved in smuggling activities in the border region for the past couple of decades is believed to be behind two mobile oil-laundering plants uncovered by Irish customs officers.
A swoop by officers yesterday morning also led to the seizure of 13 vehicles, which will now be forensically examined to determine if any can be linked to other rackets.
Supported by armed members of the garda regional support unit and local gardai, customs raided a commercial premises at Ravensdale Park in Dundalk and found a lorry that had been converted into a mobile fuel laundry.
Another flat-bed lorry had been fitted with a concealed tank to transport the fuel while two other lorries and three oil tankers were also seized.
Three oil tankers, 28,000 litres of fuel, ancillary equipment and three tonnes of toxic waste were found.
A short distance away, officers searched a private house and an adjoining yard and found a slurry tank adapted for use as a mobile oil laundry.
Officers uncovered 100 bags of bleaching earth for use in the laundering process as well as 6,000 litres of fuel, and seized three cars, two jeeps and a van.
An Irish Revenue spokeswoman said last night that investigations were ongoing and reminded the public they should be aware of the risks posed to their vehicles by using laundered fuel.
So far this year, Irish customs has seized three mobile units, capable of producing 25 million litres of fuel a year. Laundering activity had decreased this year because of the presence of extra garda patrols in the Louth-Monaghan region as a result of the murder of Det Garda Adrian Donohoe.
However, as the patrols have been reduced in the past few weeks, evidence of the laundering of oil and other illegal cross-border trade has re-emerged.
The raids were intelligence-driven and resulted from lengthy inquiries by customs and gardai in Co Louth.
No arrests were carried out, but investigators said last night they were following a definite line of inquiry.