Calls have been made for Dyfed-Powys Police to look again at the death of two siblings that shook the small community of Llangolman in the 70s, following publicity around the Cooper murder enquiry.

However, police have said the case could not be re-investigated on 'speculation alone' and would need specific new information containing detailed knowledge or evidence.

Retired farmer Griff Thomas and his sister, Martha, were found dead in their burning farmhouse at Ffynnon Samson in the village of Llangolman, in 1976.

A coroner returned verdicts of manslaughter on Mrs Thomas, aged 70, and an open verdict for her 73-year-old brother.

"At the time it was deemed 73-year-old Gruff Thomas had murdered his 70 year old sister, Patti, and then set fire to himself and that there was no third person involved," said editor of Welsh language newspaper, Clebran, Hefin Wyn.

The deaths were similar to the Scoveston Park murders where brother and sister Richard and Helen Thomas were found shot dead in their burning home in 1985, a crime John Cooper was convicted of after a cold case review in 2011.

After this conviction an investigating officer told the Western Telegraph: "We've got to look at these deaths again…the circumstances at Ffynnon Samson are identical to Scoveston Park."

Following the airing of ITV's The Pembrokeshire Murders drama, based on Operation Ottawa - which reopened and solved the Scoveston Park and Pembrokeshire Coast path cases - the call to look again at Ffynnon Samson has been made.

Clebran, in conjunction with Mynachlog-ddu Community Council, has written to Dyfed Powys Police and Crime Commissioner, Dafydd Llewelyn, seeking a review of the coroner's verdict and a possible reopening of the case.

"Llangolman inhabitants who remember the incident, and who knew the victims well, have never accepted the explanation," said Mr Wyn.

"They cannot accept that the frail brother could have acted in such a manner and they have always fuelled rumours of a third person involvement.

"With the advent of more sophisticated methods of detection, as proved in the John Cooper two double murder cases, they would welcome a re-examination of the evidence available, if only to exonerate the brother."

The letter to Mr Llywelyn states that leading forensics experts believe the evidence is worth re-examining and talks about the possibility of setting up a petition asking Dyfed-Police to do just that.

In reply he said that he had seen a copy of the coroner's report from 1976 and could 'understand why residents have concerns that some questions have not been answered'.

"There is a place to consider need to look at the cause," he said. "The question that needs to be considered of course is, are there any forensic materials available which are likely to reveal any further evidence?"

He also extended his 'deepest sympathy' to 'the family, friends and local residents of the area who have been affected by this tragic loss'.

At the Policing Board meeting this month Mr Llywelyn addressed the issue with the temporary chief constable and senior officers.

"The temporary chief constable confirmed in the meeting that Dyfed-Powys Police's stance to the matter is that they will only examine any specific new information containing detailed knowledge or evidence, and any further decisions would be based on the results of the examination of that new material," he said.

"The temporary chief constable also noted that there is no intention to re-investigate any incidents on speculation alone."