Gardai now believe the two bodies found in south Tipperary lay undiscovered for over 18 months.
The remains of 81-year-old Nicholas Smith and his 79-year-old wife, Hilary, were discovered in their remote bungalow on Monday.
Their post mortem exams were inconclusive yesterday - and Gardai are now hoping toxicology reports will establish how they died.
Southern correspondent with The Irish Times, Barry Roche, says investigators have established approximately when the English couple died.
"They believe they may have died in November or December of 2020, and lain undiscovered at the bungalow for over 18 months.
"They're basing that on some of the items found in the house, including cartons of milk in the fridge and other perishable goods that date from that period, so that's their belief that they died some time around then."
