As part of a coordinated operation by United Kingdom and Irish police, more than a dozen homes and business premises were searched in Ireland, Northern Ireland and England in connection with the kidnap and brutalisation of Kevin Lunney.
Mr Lunney, 50, was abducted outside his home near Derrylin, Co Fermanagh, and taken to a horsebox across the border, where he was savagely beaten.
The man, who was in his 50s, took ill when Derbyshire police searched his home in the United Kingdom this morning.
The father-of-six had his leg was broken, he was slashed with a knife and doused with bleach in the attack that lasted for about two and a half hours.
On the reported death in Derbyshire, Mr Harris said: "That is our understanding, but that matter happened within a search in England and that is being pursued by the authorities there".
The PSNI were searching five locations in Derrylin, Co Fermanagh, and Derbyshire Police were searching a location in England.
Mr Hamilton was speaking at Garda headquarters with Garda Commissioner Drew Harris to announce that police and prosecutors on both sides of the border had agreed to establish a landmark "joint investigation" into the intimidation campaign.
He was found over 20 miles away from his home across the border in Co Cavan after being left at a roadside.
Recounting the ordeal, Mr Lunney said he feared that he would never see his wife and children again.
Gardaí have been searching 12 locations south of the border while the PSNI have been searching five locations in the North. These premises are a mixture of domestic dwellings and commercial business premises.
Police on both sides of the border have been under mounting pressure to bring the perpetrators to justice.
The campaign against Quinn Industrial Holdings and senior staff has spanned several years.
Gardai (Irish police) said 100 officers were involved in searching five locations in County Cavan, three in County Longford and four in Dublin.
The recent abduction of Kevin Lunney represented a significant ratcheting up of things. "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".
The Quinn family have consistently condemned and distanced themselves from those attacking the new owners.
It said Sean Quinn junior had made the offer in a statement to BBC Spotlight NI.
Quinn, 71, accused QIH executives of betraying him.
QIH is a remnant of a business empire built by Seán Quinn, an entrepreneur who became Ireland's richest man before losing his fortune and companies in a bet on a toxic bank.