A former garda officer has taken over as lead investigator with the so-called Disappeared Commission.
Eamonn Henry takes over the responsibility for the day-to-day running of the organisation from Jon Hill, who is stepping down.
The commission searches for the remains of people abducted, murdered and secretly buried by republicans during the Troubles.
Its formal title is the Independent Commission for the Location of Victims' Remains.
The remains of four victims remain outstanding, while 13 have been located since the establishment of the commission in 1999.
Mr Henry is a former Garda Inspector who served for 30 years, 12 of them working in the National Bureau of Criminal Investigation.
For four years he worked as garda liaison officer with the Disappeared Commission and joined its investigation team in 2023.
"I am honoured and privileged to take up the role of Lead Investigator with the ICLVR following on from the tremendous work of the previous lead investigators Jon Hill and Geoff Knupfer," Mr Henry said.
"My commitment is to the families of the Disappeared and the ICLVR team is focused on our mission to recover the remains of all 17 victims called The Disappeared.
"Therefore I am appealing to anyone who has any information concerning the location of the remains of Joe Lynskey, Columba McVeigh, Robert Nairac and Seamus Maguire to come forward to the Commission and we will treat all information received in the strictest confidence.
"I am appealing to those persons with information to think of the grieving families who have lived with their grief for so long. It is time to return their loved ones to their families for a Christian burial."
In a statement, the commission paid tribute to Mr Hill who has been working for it since 2006.
"He allied investigative skills of a high order with his absolute determination to do everything in his power to return the remains of the Disappeared to their families.
"Beyond that he formed a close bond of trust and affection with the Families of the Disappeared."
Mr Hill said he informed the commission last year of his intention to step down, saying he had found it increasingly difficult to balance his work and home life.
He said he was proud to have been part of the commission's successes.
Anyone with information on the four outstanding Disappeared cases can contact the ICLVR on 01 602 8655, by email: secretary@iclvr.ie or ICLVR PO Box 10827 Dublin, Ireland.
