UK police say the man took ill while a search was being carried out in Derbyshire this morning.
A man suspected of being involved in the abduction and assault of Quinn Industrial Holdings director Kevin Lunney has died in the UK.
Derbyshire police say the man in his 50s took ill while a search was being carried out in Derbyshire this morning.
The search was being conducted as part of a wider operation throughout the Ireland and the UK.
More than 100 Gardai are continuing to search homes and businesses across Cavan, Longford and Dublin.
Meanwhile, the PSNI is also searching four homes and a business in Derrylin, Co. Fermanagh.