Four more arrests have been made by gardaí investigating the abduction and torture of Quinn Industrial Holdings executive Kevin Lunney.
The 50-year-old was savagely beaten after being taken from outside his home near Derrylin in Co Fermanagh and transported across the border.
He was found with serious injuries dumped by a roadside in Coranafean, Co Cavan.
His leg had been broken in two places, his face had been sliced with a Stanley knife, QIH was carved on his chest, and he had been doused in bleach.
Two men, both aged 38, are being detained at Ballymun and Finglas Garda stations.
A 25-year-old man is being held at Irishtown Garda station, and a 66-year-old man is being held at Monaghan Garda station.
Last week, two men and a woman arrested by gardaí in relation to the attack were later released without charge.
A convicted criminal considered a key suspect died earlier this month during a police raid in England.
Cyril McGuinness suffered a heart attack while Derbyshire Police were searching a house where he was staying in the Buxton area.
The attack on Mr Lunney, during which his assailants demanded his resignation, was the most serious of a five-year campaign of intimidation targeting the companies and directors that now control the business that was built up by fallen tycoon Sean Quinn, once Ireland’s richest man.
A sinister element in the community in the Fermanagh/Cavan border area, where the companies are based, continues to vent anger at the demise of Mr Quinn’s empire.
The Quinn family has consistently condemned and distanced itself from those responsible.