The Acting Garda Commissioner has said gardaí have made significant progress in the investigations into the deaths of three young people in the last two weeks.
Separate investigations are under way into the murders of Anastasia Kreigel, Jastine Valdez and Cameron Reilly.
Anastasia Kriegel, 14, was found dead at an abandoned farmhouse outside Lucan on Wednesday 16 May.
She had been reported missing from Lucan, Co Dublin the previous Monday. A 13-year-old boy has been charged with her murder.
The body of Ms Valdez, 24 and from Enniskerry in Co Wicklow, was discovered in thick undergrowth in the Puck's Castle area of Co Dublin on Monday 21 May.
Mark Hennessy, 40, from Bray is suspected of kidnapping and strangling her in an apparently random attack in Enniskerry.
Mr Reilly, 18, was found dead at Riverdale, Dunleer, Co Louth at around 8am on Saturday 26 May.
He had last been seen in the vicinity of Ardee Road, Dunleer in the early hours of that morning.
Searches as part of the investigation are continuing in Dunleer and gardaí are still looking for Mr Reilly's mobile phone.
They are appealing to anyone who has information to come forward, as they believe there are people in the locality who have information.
Gardaí have spoken to a number of people who were with Mr Reilly on Friday night and they also have CCTV from a local takeaway.
It is understood that Mr Reilly was there at around 12.30am on Saturday morning and a row may have broken out outside the takeaway.
Gardaí are trying to speak to some of Mr Reilly's friends to try to ascertain what happened after that.
Joe Torris, a friend of the Reilly family, made an emotional appeal for information.
Speaking to RTÉ News, he said: "If you have seen something and you’re scared, step up. Say it to me. Say it to a guard. Say it to your teacher. Say it to your parents. Say it to your guardians.
"If you were there, if you were talking to somebody who was there, step forward. We need to be brave now, we need to stop this."
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Acting Commissioner Dónall Ó Cualáin has said one would not expect crimes of this nature to happen in such a short space of time, and he described the grouping as unusual.
He said that much of the focus in recent time has been on so-called gangland killing, and these deaths were of a different type.
Mr Ó Cualáin said it was important that gardaí get to the bottom of the three cases and thanked the public for their help in the investigations.