A man has died during a search in Derbyshire in connection with the abduction and torture of Kevin Lunney.
Cyril McGuinness, aged in his 50s, is believed to be one of the main suspects involved in the attack on Mr Lunney in September.
Police raided the home in Buxton on Friday.
50-year-old Mr Lunney was abducted and brutally tortured in an attack on September 17 while he was driving home from work in Kinawley, Co Fermanagh.
He was found over 20 miles away from his home across the border in Co Cavan after being left at a roadside.
The father-of-six had his leg broken in two places, was doused in bleach and cut with a stanley knife in the horrific ordeal which he recently recounted in a BBC NI Spotlight programme.
Police say searches are being carried out at four residential properties and one commercial premises in Derrylin.
An Garda Síochána are searching five locations in Co Cavan, three locations in Co Longford and four locations in Dublin. These premises are a mixture of domestic dwellings and commercial business premises.
Derbyshire police are also conducting a search in England.
PSNI's Detective Chief Inspector Mullan said: "This was a truly horrific crime and we continue to work closely with our colleagues in An Garda Síochána and now also Derbyshire Constabulary to try and bring the perpetrators to justice."
Meanwhile, a new security hut has been installed at Quinn Industrial Holdings' (QIH) headquarters in Derrylin where Mr Lunney and other executives work.
QIH released a statement welcoming the investigation.
A spokesperson said: "QIH welcomes the joint investigative effort evident in this morning’s coordinated searches by Gardai, the PSNI and Derbyshire Constabulary.
"The searches mark an important milestone in bringing those involved in attacks on QIH staff to justice.
"We encourage anyone with information to make contact with the gardai or PSNI on a confidential basis."