Minister for Justice Helen McEntee has expressed her sadness as the sixth search for disappeared teenager Columba McVeigh ended without success.
The 19-year-old from Donaghmore, Co Tyrone was abducted by the Provisional IRA, killed and secretly buried in 1975.
The Independent Commission for the Location of Victims’ Remains (ICLVR) has now conducted six unsuccessful searches at Bragan Bog in Co Monaghan since 1999, covering more than 26 acres.
A fresh appeal for information has been made in a bid to narrow down where he may have been buried.
Mr McVeigh’s sister Dympna Kerr said she is “totally heartbroken”, adding: “I don’t know how many more times I can go through this”.
“All we need is for people to come forward with the correct information – there is nothing for them to fear,” she told the BBC, adding she cannot give up hope that one day her brother will be found.
Ms McEntee said she had held out hope that the latest search would find Mr McVeigh, despite “extremely challenging” conditions at the isolated Bragan Bog site.
“I am saddened that, in spite of the substantial efforts of the commission, the remains of Columba have not been located at Bragan Bog,” she said.
“I want to acknowledge the unwavering and sustained determination of the Commission to locating Columba since the first search at Bragan Bog was conducted in 1999. I would like to thank the investigators, forensic archaeologists and machine contractors for their painstaking and sensitive work.
“Today, my thoughts again are with the family of Columba who have endured this particular cruelty for so many years.”
She added: “Ireland’s national Missing Persons Day will fall on December 6 this year and at this time we think of all families of The Disappeared who still await the return of their loved ones’ remains.
“The role of the commission is a critical humanitarian one: to support these families who have suffered the devastating loss of their loved ones.
“This government remains steadfast in its commitment to supporting the ongoing work of the commission.”
Seventeen people were disappeared by republican paramilitaries during the Troubles.
The remains of Mr McVeigh, former monk Joe Lynskey, British Army captain Robert Nairac and Seamus Maguire, who was in his mid-20s and from near Lurgan, Co Armagh, have never been recovered.
The ICLVR can be contacted by telephone: 00800-55585500 International: +353 1 602 8655, email to Secretary@iclvr.ie or by post to: ICLVR PO Box 10827.