Human remains have been found during the search for one of the "Disappeared", Peter Wilson.
The Independent Commission for the Location of Victims Remains confirmed that the remains were found at a site in Waterfoot, County Antrim.
A spokesperson said the recovery was ongoing and the formal identification process would take some time.
Peter Wilson was 21 when he went missing from his home in the Falls Road area of west Belfast in 1973.
He is believed to have been abducted and murdered by the IRA.
The commission has overseen the discovery of seven bodies and numerous searches since it was set up in 1999 to locate those murdered and buried in secret graves by republican paramilitaries during the troubles.
Peter Wilson's family had just attended a walk at Stormont in memory of the 'Disappeared' when a call came through at about 1330 BST to say his remains had been found.
His sister, Anne Connolly, said it was a shock to learn recently that he might be buried there as her mother, Lily, who died three years ago, often sat on Waterfoot beach.
She spoke of a "mixture of relief, and great sadness" to learn that his body had been found so soon after the dig began on Tuesday.
Archaeologists and other experts had been examining the beach at Waterfoot in the Glens of Antrim.
The investigation by the ICLVR was launched following a tip-off.
Remains found in County Monaghan in July were confirmed as being those of Crossmaglen man Charlie Armstrong, a 57-year-old father-of-five who went missing on his way to Mass in 1981.
In October, human remains believed to be those of Mr Armstrong's neighbour Gerry Evans were found at a site in County Louth.
Sinn Fein president Gerry Adams said he welcomed reports of remains being found at Waterfoot.
"My thoughts are with the Wilson family at this time and I would hope that confirmation would be speedy to ease the burden of the final wait the family will endure," he said.
"I again would repeat my appeal that anyone with any information which might help other families locate remains and find closure should bring that information forward."
SDLP MLA, Declan O'Loan said the finding of the body would be a huge relief to the family of Peter Wilson, "even though they still have to await a formal identification process".
"The local community, who have been gathering in the evenings at Waterfoot to pray for a successful search, will also find great comfort in this find as the entire operation has had an immense impact on people in this area," he said.
"I would like to congratulate the ICLVR on their efforts to carry out this search and their successful outcome and I appeal to people who have any information about the whereabouts of other bodies to pass it onto the authorities as soon as possible."