CUSTOMS investigators in the Republic have charged a man from Northern Ireland.
It follows the discovery of two fuel laundering plants in Co Monaghan on Monday.
The 27-year-old man from Armagh was arrested after a raid at Killyneill, less than a mile from the border.
He was taken away to be questioned at Monaghan Garda Station.
The suspect is to appear later on Tuesday at Virginia District Court in Co Cavan.
Investigators discovered the plants in a private yard and a commercial premises and could six million litres of diesel a year.
That amounts to a loss to the Republic’s public purse of £2.9 million (€3.5 m).
A diesel laundering plant was found at one of the premises when it was raided by customs officers last year.