Information passed to the Independent Commission for the Location of Victims Remains earlier this year has led to fresh searches for the body of south Armagh man Gerard Evans.
It is alleged the IRA abducted the then 24-year-old as he was hitching a lift home after a night out in 1979 before killing and dumping him in the bogland at Carrickrobin, Co Louth.
While the IRA leadership has denied involvement, a purported member of its south Armagh brigade told a Sunday newspaper he was part of a 12-member team who carried out the killing.
The revelation sparked a geophysical survey and drainage of the land near Hackballscross, part of which was under water.
The area has been divided into grids and an archaeological 'time-team' headed up by top scientific detective Geoff Knupfer are now excavating particular areas based on the results of the survey.
But an ICLVR spokesman cautioned against hopes of an immediate breakthrough, pointing out that investigators were onsite in the Wicklow Mountains for 18 months before recovering the remains of Disappeared victim Danny McIlhone last year.
"There won't be large scale excavation but there will be clearance of some soil," he said.
"We'll be there for as long as it takes but we expect to be there for a considerable period."
Last month, scientific detective Geoff Knupfer said direct contact with the IRA led to a breakthrough in finding Mr McIlhone's remains, at isolated bogland on the side of Wicklow's second highest peak, Mullaghcleevaun.
Information to the ICLVR, set up by the Irish and British governments to locate the remains of the Disappeared, was previously being fed through intermediaries, according to the former Greater Manchester detective who helped find the bodies of Moors murderers Ian Brady and Myra Hindley's child victims.
However, security sources warned that direct talks do not automatically guarantee every remaining body will be found.
Disappeared
There are now 14 Disappeared - people who were abducted, murdered and secretly buried by republicans.
A total of five of them, Eamon Molloy, Brian McKinney, John McClory, Jean McConville and Danny McIlhone, have been found.
The IRA admitted in 1999 that it murdered and buried nine of the victims - Seamus Wright, Kevin McKee, Ms McConville, Columba McVeigh, Brendan Megraw, Mr McClory, Mr McKinney, Mr Molloy and Mr McIlhone - in secret locations.
Others who vanished during the conflict include Mr Evans, Charles Armstrong, Robert Nairac - who are also thought to have been murdered by the IRA - and Seamus Ruddy, who disappeared in France and whose murder was admitted by the splinter republican group the Irish National Liberation Army.
Excavations and surveys are also being carried out at Colgagh, Co Monaghan, for the remains of Charlie Armstrong; at Coghalstown, Co Meath, for Seamus Wright and Kevin McKee; and at Oristown, Co Meath, for Brendan Megraw.
It is understood a search for IRA victim Columba McVeigh at Bragan, Co Monaghan, is also nearing an end.
Earlier this month west Belfast man Peter Wilson, 21, who vanished from his home in 1973, may have become the latest IRA abduction victim.
But a senior republican source has since denied the organisation was involved in his disappearance.
A week ago families of the Disappeared gathered to lay a wreath at Stormont and issue a fresh appeal for information.
