Northern Ireland police have arrested a man over the shooting dead of 10 Protestant textile workers in 1976 in one of the deadliest of three decades of sectarian attacks in Northern Ireland.
No one has ever been convicted for the crime, which an inquiry said was carried out by the Provisional IRA who targeted the men because of their religion.
The IRA has always denied involvement in the attack near the village of Kingsmill, county Armagh, in January 1976, when gunmen forced workers from a minibus and shot them dead at close range.
The one Catholic worker was instructed to run from the scene.
The incident was one of a series of tit-for-tat attacks by Protestant loyalist paramilitaries who wanted Northern Ireland to remain part of the United Kingdom and Catholic Irish nationalists who wanted a united Ireland.
A 1998 peace agreement paved the way for a power-sharing government of loyalists and Irish nationalists and mostly ended the cycle of violence, though some small armed groups remain.
Police on Friday said they had arrested a 59-year-old man in Newry on suspicion of the murders.
Investigators earlier this year found a match with a palm print found on a getaway car.
Investigations of historic crimes have in the past caused tension between the governing parties, which include former militants.