Three people arrested by detectives investigating the kidnap and torture of Co Fermanagh businessman Kevin Lunney have been released unconditionally.
The two men, aged 23 and 61, and one woman, aged 61, were detained in the Fermanagh area on Thursday on suspicion of conspiracy to kidnap; conspiracy to cause grievous bodily harm with intent; and assisting offenders.
The Police Service of Northern Ireland announced their release from custody in Omagh police station on Friday.
In the Irish Republic on Thursday, the Garda arrested a man in his 30s in relation to the abduction and assault. He was detained at Cavan Garda station. Gardai said he remained in custody on Friday.
Mr Lunney, a director at Quinn Industrial Holdings (QIH), was abducted outside his home near Derrylin, Co Fermanagh last September and taken to a horsebox across the border, where he was savagely beaten.
His attackers broke his leg, sliced his fingernails and face with a Stanley knife, carved QIH on his chest, and doused the father of six in bleach. They demanded his resignation during the ordeal.
The attack was the most serious in a six-year campaign of intimidation targeting the companies and directors that now control the business portfolio which was built up by fallen tycoon Sean Quinn, once Ireland’s richest man.
The Quinn family has repeatedly condemned the intimidation.
The Garda and PSNI established a joint investigation team to work on the case last November.
A serial criminal considered a key suspect in the kidnapping and torture died from a heart attack when police arrested him in Buxton, Derbyshire, last November.
Cyril McGuinness, known as Dublin Jimmy, was believed to have been hiding out in the area following the assault.
In December, four men were remanded in custody at a court in Co Cavan charged with the kidnap and torture of Mr Lunney.