The PSNI has made another arrest in connection with the murder of Jean McConville in 1972.
The suspect was originally detained by officers last month but the interview process was halted due to a medical issue arising.
The man presented himself at Antrim police station this morning.
Seven people have been detained and questioned in the last two months in connection with the 1972 murder - the most high profile being Sinn Féin president Gerry Adams.
Mr Adams (65) was released on Sunday without charge after four days in police custody. A police file is to be passed to prosecutors to determine whether any charges will be pursued. Mr Adams vehemently denies any involvement in the crime.
In March veteran republican Ivor Bell (77) from Ramoan Gardens in west Belfast, was charged with aiding and abetting the murder and IRA membership.
Police are preparing files on four women also detained in connection with the murder for Northern Ireland’s Public Prosecution Service.
Mrs McConville was dragged, screaming, away from her children in the Divis flats in west Belfast by a gang of up to 12 men and women after being wrongly accused of informing to the security forces.
The 37-year-old widow was interrogated, shot in the back of the head and then secretly buried - becoming one of the 'Disappeared' victims of the Troubles. Her body was not found until 2003 on a beach in Co Louth, 50 miles from her home.
A Police Service of Northern Ireland (PSNI) spokesman said: "Detectives from Serious Crime Branch investigating the abduction and murder of Jean McConville in 1972 have arrested a 56-year-old man in Co Antrim. He is being questioned in the Serious Crime Suite at Antrim police station."