A 77-year-old is being questioned about the murder of Jean McConville, who was abducted, shot dead and secretly buried by the IRA more than 40 years ago.
The man was detained at his home in the Andersonstown area of west Belfast at lunchtime.
Police later confirmed he was taken to the custody suite at Antrim to be interviewed by officers belonging to the PSNI’s serious crime branch.
Mrs McConville, a 37-year-old mother-of-ten, was seized at her home at Divis Flats beside the Falls Road in Belfast by an IRA gang in December 1972.
She had been accused of passing information to the British army. An investigation later carried out by the Northern Ireland Police Ombudsman emphatically rejected the allegations.
Nobody has ever been charged with the murder, which was one of the most notorious in the history of the Northern Ireland troubles.
Police said they could not comment further on the arrest, but it is believed officers were acting on some sort of new information.
Mrs McConville was a Protestant who converted to Catholicism after she married a Catholic man, a former British soldier.
She was kidnapped by up to a dozen IRA men and women and later shot in the back of the head and then buried 80km from her home.
The IRA did not admit her murder until 1999 when information was passed on to gardaí.
Mrs McConville became one of the so-called Disappeared, but it was not until August 2003 when her remains were eventually found on Shelling Hill beach, Co Louth.