An investigation into the deaths of 10 Protestant textile workers is to be reopened.
It comes after the discovery of new evidence and eight days after an inquest began into the Kingsmills Massacre.
The hearing in Belfast has learned of the discovery of a palm print found on a getaway vehicle which may be linked to fingerprints.
The decision to reopen the investigation will come as a major relief to the families of those who died.
They have long campaigned for justice for their loved ones, who were lined up and shot by the side of the road at Kingsmills on January 5, 1976.
The IRA carried out the killings, one of the worst atrocities committed here, but nobody has ever been convicted.
Ulster Unionist MLA Danny Kennedy has welcomed the discovery of new fresh evidence, but cautioned that the investigation had to be fully resourced and completed as soon as possible.
Mr Kennedy said: “I welcome the discovery of new evidence which has led to the re-opening of the police investigation into Kingsmills. “Kingsmills was a brutal and barbaric crime and I sincerely hope that the police now have a realistic prospect of mounting a successful prosecution of some of those responsible.
“Bearing in mind that the inquest only opened last week, it is imperative that the police investigation is properly and fully resourced with a view to completing it as a matter of urgency.
“There is a saying that ‘justice delayed, is justice denied.’ The families and sole survivor have waited forty years and this fresh investigation must not be used in any way as a further delaying tactic to hamper their pursuit for maximum truth and justice.”
DUP MLA William Irwin has said the revelation was a major step forward but questioned how such a major piece of evidence could wait 40 years before being properly investigated.
He said: “This was a brutal sectarian massacre carried out in cold blood and the revelation that such a key piece of evidence has lain untouched for four decades will deepen the pain of relatives who have waited so long for justice.
“Now that this process is underway it is vital however that the investigation is carried out quickly and thoroughly. The families deserve to see justice served and to know that all avenues have finally been pursued to bring those responsible to justice.”
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