GARDAÍ will travel to the UK and the US to interview three women about the murder of teenager Raonaid Murray in 1999 as part of an ongoing cold case review of the unsolved killing.

Raonaid Murray (17), was stabbed to death while walking home in Glenageary, south Dublin, in 1999. Two years ago, the gardaí's serious crime review team, commonly known as the cold-case unit, began a renewed investigation of the murder.

It is understood the investigation, in conjunction with local gardaí in Dun Laoghaire, is progressing well. The three women, two living in the UK and one in the US, were all acquaintances of the teenager. A source played down the significance of garda plans to re-interview these women, saying gardaí believe these women could have more information that could help advance garda enquiries and are not necessarily suspects.

These three women did not leave Ireland in the immediate aftermath of the teenager's murder but relocated in recent years.

The original garda investigation was extensive. More than 8,000 statements were taken and 3,000 people were interviewed. Because of the sheer volume of statements taken, its review is still ongoing although it has made a number of recommendations.

In September 2009, gardaí launched a public appeal to try and identify two people seen near the murder scene around the time the 17-year-old was stabbed to death. Gardaí said the two people, a man and a woman, were "people of interest" in the investigation. However, these people have still not been located by gardaí.

A number of people have been questioned but no one has ever been charged. No clear suspect has ever been identified.

Murray's body was found by her older sister, Sarah, on a road close to her home at Silchester Crescent, Glenageary, south Co Dublin, in the early hours of Saturday, 4 September 1999. She had been stabbed repeatedly nearby and bled to death.

The cold-case unit had its first major success in July when a case it reviewed led to a conviction. Vera McGrath (61) was sentenced to life in prison after being found guilty of murdering her husband Brian McGrath at their Westmeath home 23 years ago.