Gardaí 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 gardaí are now hoping toxicology reports will establish how they died.
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Southern correspondent with The Irish Times, Barry Roche, says investigators have established approximately when the English couple died: