Families of missing people are being asked to provide DNA samples to try to solve hundreds of cold cases dating back almost 70 years.
According to gardaí, there are still 813 people who have been reported missing in Ireland whose cases have not yet been closed. The outstanding cases date to 1951.
A national DNA database, set up five years ago, has been credited with bringing a number of long-term missing persons cases to a close. The database, which is used to solve a wide range of crimes, relies on a voluntary DNA sample from a person's family to solve a missing person's case.
"The majority of persons reported missing return soon after their disappearance without suffering any harm," a spokeswoman for An Garda's Missing Persons Bureau said.
"A small percentage may come to harm or may be the victim of crime. A missing persons investigation will remain open until the missing person has been located irrespective of the time passed."
The unit has called on families of missing people to provide DNA samples.
"It is beneficial that family members of missing persons provide a DNA profile in long-term missing persons investigations.
"Parents, siblings and children of missing persons can provide a DNA sample to An Garda Síochána which will be uploaded on to the Missing Persons Database."
The Missing Persons Database, managed by Forensic Science Ireland (FSI), was set up in 2015 and has been described by the DNA lab as "one of the most important crime-fighting tools introduced within the State in recent times".
In 2018, it started using the "pedigree tree approach", which means using family tree DNA to help identify the remains of missing people.
Operation Runabay, which was launched in 2017 by the Missing Persons Bureau, aimed to collect DNA samples to identify remains found along the west coast of Great Britain that may belong to people who went missing in Ireland.
Last year, it helped solve the case of Conor Whooley, a 24-year-old man who vanished from Dublin in August 1983. His remains were identified in a graveyard in Wales.
In 2018, the DNA database helped to identify five missing people, which FSI said brought "much-needed closure to their families and friends". The FSI had developed new technology that helped it identify DNA from bones, including ones which had been recovered from water. This meant bodies that had been recovered years before but could not have DNA samples taken could finally be identified.
The body of Aengus (Gussie) Shannon, who went missing from Limerick in 2000, was identified 18 years later. Bones had been found in the River Shannon in October 2001, but until 2018 it was impossible to take a DNA sample from them.
In November 2018, it was announced the technology had successfully identified the remains of two more long term missing persons.
Margaret Glennon, a 49-year-old mother of four, went missing from her home in Baldoyle, north Dublin, in 1995. Remains discovered by a JCB driver in Malahide in 2014 were confirmed as hers using the new technology in 2018.
The disappearance of James Gallagher, an 18-year-old from Cabra who went missing in February 1999, was also solved. It was confirmed that remains discovered in Dublin in 2002 were his.
In the same year, FSI also worked with two international police forces to identify the remains of two other missing people.
A body found on a north Wales beach 33 years previously was finally identified as that of Joseph Brendan Dowley, a 63-year-old man from Kilkenny who was last seen boarding a ferry from Ireland in October 1985.
The following month, unidentified remains were discovered washed up on Rhosneigr beach in Anglesey. The Garda Missing Persons Bureau worked with North Wales Police to exhume the remains before confirming they were those of Mr Dowley.
Paul Shine-Dixon (28), from Finglas, went missing while on his way to meet his partner in Barcelona in 2009. He was travelling through Europe by train when he got off in the French city of Perpignan on May 2. His remains were found buried near a canal in Perpignan in 2018. Garda used the national DNA database to work with French authorities to identify his remains.
In December 2018, the national forensic science lab used a National Missing Persons Day event to collect DNA from families of missing people. It was part of a plan to continue using DNA to solve cold cases.