The Commission for the Location of Victims Remains (ICLVR) has confirmed it is calling off a search for a man missing since 1979.
It has spent 18 months looking for the body of Gerry Evans who was last seen in Castleblayney in County Monaghan.
The search has been focused on Carrickrobin in County Louth.
Geoff Knupfer from the ICLVR said he was certain the site had been searched thoroughly and that if the remains were there, they would have been found.
The lengthy duration of the search was partly caused by flooding at the site, which meant that drainage equipment two and a half miles long had to be installed.
Mr Knupfer said that his thoughts were with Mr Evans' family.
He added: "It must be heartbreaking for them that we have come to the end of this process now and we have not found Gerry."
Meanwhile, the head of a forensic archaeological team that works alongside the ICLVR, has said that it is awaiting the go-ahead to begin work on a new site.
John McIlwaine said the site to be investigated was in the "north of Ireland" and a search would begin once clearance was given.
It is believed the search would be for the body of the Belfast man, Peter Wilson.
The 21-year-old, who had learning difficulties, went missing from his home in west Belfast, in 1973.
His name was added to the list of names registered with the Commission in November last year.
If the team gets clearance, it would be the first time that a dig for one of the disappeared has taken place in Northern Ireland, with all other searches having been carried out in the Republic.
However, Mr Knupfer declined to confirm the development.
He said: "There are 16 cases on the commission's books and several of them are ongoing enquiries. As and when we are in a position to start another operation on a site, we will announce it."
In June 2010, Mr McIlwaine led the forensic archaeology team which discovered the remains of Charlie Armstrong.
Mr Armstrong, 57, who was from south Armagh went missing on his way to Mass in 1981.
He was believed to have been kidnapped and murdered by the IRA.
His body was buried in an area of peat bog land at Colgagh, County Monaghan, several miles from the border.
Mr Evans' family lived in Crossmaglen, County Armagh, a few doors from the home of Charlie Armstrong.
The ICLVR was established by a treaty between the British and Irish governments in 1999 following the Good Friday Agreement.
Its purpose is to obtain information in strictest confidence which may lead to the location of the remains of "the Disappeared" - those killed and buried in secret by banned paramilitary groups prior to 10 April 1998 as a result of the Troubles.
Sixteen people were murdered by republican paramilitaries and secretly buried in isolated parts of Ireland during the Troubles.
Nine bodies of the people known as the Disappeared remain unfound.
In 1999 the IRA admitted responsibility for killing and secretly burying nine of the 16, while one was admitted by the INLA.