The prominent dissident Irish republican Colin Duffy has been released from police custody after detectives questioned him about the murder last week of a Northern Ireland prison officer.
Duffy and a 31-year-old man also arrested in Lurgan, County Armagh, shortly after the killing of David Black were freed from custody. However, a 29-year-old man arrested in the Irish Republic in connection with the murder is still being questioned by the Garda Síochána.
The US secretary of state, Hilary Clinton, joined Irish politicians, north and south, at the weekend in condemning the killing, describing it as a cowardly act.
Black will be buried on Tuesday in Cookstown, County Tyrone, after a service at his local Presbyterian church.
The 52-year-old died after he was shot during a drive-by ambush on the M1 motorway last Thursday morning. The father of two had been driving from his home to work at Maghaberry top-security prison when his Audi car was raked with automatic gunfire.
He was the first prison officer to be murdered by paramilitaries since 1993. There have been tensions between prison authorities and 41 dissident republican inmates held in Maghaberry.