An autopsy has revealed Walter Plunkett died of asphyxiation and compression of the chest.
A 50-year-old woman, who was known to the victim, was arrested at the scene.
She was held overnight at Enniscorthy Garda Station after undergoing psychiatric medical treatment at Waterford Regional Hospital.
The investigation is being co-ordinated by John Roche, chief superintendent of Wexford Garda Station, and Insp Pat Coady of Enniscorthy Garda Station.
Chief Supt Roche said the investigation had been “upgraded” as a result of the autopsy. While he declined to elaborate, a statement last night from Garda headquarters made clear it was a murder probe and that gardaí were not seeking any other person in relation to the man’s death.
Mr Plunkett, a widower from Ballyedmond, Monamolin, Co Wexford, died outside his home at about 4.50pm on Sunday.
Officers from Enniscorthy Garda Station had found him lying on the front lawn. Medical assistance was summoned but Mr Plunkett was pronounced dead at the scene.
The autopsy was carried out at Waterford Regional Hospital yesterday by Professor Marie Cassidy, the state pathologist.
The woman was arrested on Sunday night and taken to Enniscorthy Garda Station for questioning.
Mr Plunkett previously lived in England, but on his return to Ireland about 20 years ago went to reside with his wife and daughter in Ballyhea. His wife died in 1995, after which he became known to the woman at the centre of the investigation.
Neighbours described the 81-year-old as a gentle and kind man who was still very active.
“He still continued to drive his car. A very inoffensive and kind man, who was well known and like in the area,” said one neighbour.
Yesterday, neighbours and friends who met at a pub in Ballyedmond less than 200m from Mr Plunkett’s home, spoke of their sadness at his death.
One mourner said: “A black cloud hangs over the area as this is a very close- knit community. We have never experienced a tragedy like this in the area. We are all in shock.”