A man has been arrested following the death of Thomas O'Hare, who was doused with petrol and set alight along with his partner at their home outside Keady in south Armagh on Monday.
The PSNI said yesterday that the man was arrested on "suspicion of murder and attempted murder". A spokesman said that the man being questioned was being held in Northern Ireland. He declined to comment further.
Mr O'Hare (33) died in Belfast's Royal Victoria Hospital in the early hours of yesterday following the arson attack at a house on Foley Road in Keady, in which police believe up to six people were involved.
The dead man's partner, Lisa McClatchey (21), who also sustained serious burns, remains critically ill in hospital.
Four brothers are being treated for serious burns in St James's Hospital in Dublin, after they turned up at a hospital in Co Louth.
They are expected to be questioned about the arson attack but they are too ill to be interviewed at this stage.
It is understood that their treatment, for 35 per cent to 55 per cent burns, will take some time. Mr O'Hare died after failing to recover from his injuries.
Detectives are also believed to be investigating unconfirmed reports that he was threatened before the attack at his home on Foley Road.
Reports suggest the PSNI has already carried out a house search in connection with the inquiry and they are anxious to interview a woman.