Investigators who have uncovered remains in a search for one of the Disappeared say two bodies have been found in a single grave.
The Independent Commission for the Location of Victims' Remains (ICLVR) initially thought the remains found at a bog in the Republic of Ireland on Thursday were those of Joe Lynskey.
He was abducted, murdered and secretly buried by the IRA in 1972.
There was "surprise", an investigator said, when another body was found.
Two more of the Disappeared, Seamus Wright and Kevin McKee, were believed to have been buried close to the site that was being searched in Coghalstown, County Meath.
The term the Disappeared refers to victims who were murdered and secretly buried by republicans during the Northern Ireland conflict.
Geoff Knupfer, the head of the ICLVR investigation team, said the "assumption" was that the first body discovered was that of Mr Lynskey.
"But as our archaeologists continued to excavate they found further remains in the grave," Mr Knupfer said.
"Because there are two people in the same grave, clearly there's a distinct possibility that what we have here are the remains of Seamus Wright and Kevin McKee.
"But that remains to be seen.
"So, we're just saying that we have two victims in the same grave, which fits the profile of the Wright and McKee abduction and murder," he added.
Mr Knupfer also said that an adjoining plot of land had been searched "some years ago" for the bodies of the two men.
While the remains have not yet been identified, Mr McKee's sister Maria said she was feeling a mixture of emotions after being informed that one of the bodies could that of be her brother.
"It's a happy time, but it's also going to be a sad time," Ms McKee said.
"The sad thing about it is my mummy only missed it by three years. On her deathbed she did ask for Kevin.
"It's unreal, it's surreal to us."
Jon Hill, a senior investigator, said that due to the passage of time there could have been confusion among those who had provided information to the ICLVR on the where bodies of the Disappeared had been buried.
"It's so long ago that this happened and this ground where we're searching has changed dramatically from when these events occurred," he said.
Kevin McKee and Seamus Wright were both IRA members who were abducted and murdered by the organisation in 1972.
Mr Lynskey had been a former Cistercian monk from the Beechmount area of west Belfast, and later joined the IRA.
Once the remains have been recovered, they will be taken to Dublin for examination by the state pathologist.
Mr Hill said it would be "some weeks before the DNA can give some more clarity" as to whose bodies had been uncovered.
Maria Lynskey, a niece of Mr Lynskey, had travelled to the site after the initial discovery.
Anne Morgan, the sister of another of the Disappeared, Seamus Ruddy, has been supporting the Lynskey family.
She said Ms Lynskey had "thought the whole day that it was her uncle" who had been found, but has "come to terms" with indications that now may not be the case.
Excavations had started at the bog in March in a search for Mr Lynskey.
Mr Knupford said that if it transpired that his body was not among those that had been found a search of the site would continue.
The ICLVR was set up by the British and Irish governments in 1999 to liaise with former paramilitaries to find the Disappeared.
Any information provided to the commission cannot be used in criminal proceedings.
Over the past 16 years, the ICLVR has searched for 16 people who were officially listed as the Disappeared.
The remains of 10 of the victims have been recovered and formally identified to date.
The most recent confirmed discovery was that of Brendan Megraw, whose remains were found in Oristown bog, also in County Meath, last October.