The description of a man and a woman has been issued by gardaí who want to interview them in connection with the investigation into the death of Raonaid Murray in 1999.
The 17-year-old was stabbed to death near her home ten years ago today.
The man who is described as in his 20s with short black hair, 5'10" and was wearing dark clothes when he was seen on Silchester Road near the murder scene at around the time Raonaid was stabbed to death.
The woman who was seen about ten to 15 minutes later nearby is described as between 16 and 23 years of age, 5'6" with dark shoulder-length hair.
Gardaí have not ruled out the possibility that the man and woman may have been together.
Detectives say these people are significant to the investigation and they need to speak to them to eliminate them from their inquiries.
It is the first time the investigation team has sought help to identify these people.
The officer leading the investigation, Detective Superintendent John Mulligan, also appealed to the killer to contact gardaí.
He said this person must be carrying a burden and would be treated humanely and with dignity.
Det Supt Mulligan said it would enable gardaí to give some comfort to the Murray family and bring this matter to a close.
Meanwhile, gardaí say they are satisfied the teenager was not killed by Farah Swaleh Noor, who was subsequently killed and dismembered by sisters Charlotte and Linda Mulhall at their mother's home.
He was for some time a suspect for the murder but detectives say they are now satisfied he was not involved.
Gardaí insist they are still diligently pursuing the killer of the 17-year-old and the case has been investigated by the Serious Crime Review Team.