Two men and a woman have been found dead at a property in Co Louth.
Gardai said one man had been arrested after they were alerted to a “serious incident” in Tallanstown on Monday morning.
Those who died are understood to be from the same family.
Ireland’s Justice Minister Jim O’Callaghan said there was no further threat to the public following the “criminal act”.
A gardai statement said: “Three people – two males and one female (all adults) – were found deceased at the scene.
“The scene has been preserved for technical examination.
“The offices of the coroner and the state pathologist have been notified.
“A male, aged in his 30s, has been arrested and is currently detained at a station in the Garda North West Region under Section 4 of the Criminal Justice Act 1984.”
The statement said investigations were ongoing.
Gardai have closed a road leading to an isolated property at the scene.
A blue and white forensic tent has been set up close to the property.
Gardai and forensic investigators in white overalls were present at the scene.
One neighbour told the PA news agency it was a “shocking” incident.
Mr O’Callaghan said: “I have information, An Garda Siochana have passed on information that I have received to the office.
“I am conscious that it is a developing story and it is a sensitive issue but there is no further information I can put into the public domain at present.
“I think further information will become available in due course.”
He added: “What I can say and what gardai have said is that they are not looking for anyone else in respect of this criminal act.
“There is no ongoing threat to the public in Co Louth.”
Speaking to PA at the scene, Sinn Fein TD Ruairi O Murchu said there was “shock” and “disbelief” around the area.
“There are no words – this is beyond shocking. We’re talking three within the one family that are dead.”
Mr O Murchu said neighbours were “taken aback”, adding: “My heart goes out to the family and the wider community.”
He said: “This is absolutely rural mid-Louth, nobody was expecting what we heard today.”
He appealed for members of the public to provide assistance to gardai if they can and discouraged people from participating in speculation.
Also at the scene, Fianna Fail councillor John Sheridan said the family involved was “well known and respected” in the area.
“They were very much seen a lot, that’s probably what makes this all the more shocking.”
Mr Sheridan said the area was close and very typical for a “remote and rural area”.
He warned that while the news was shocking, there was some unhelpful speculation around the incident.
Fine Gael councillor Rachel Kerley told PA: “This morning there was complete and utter devastation as the news filtered through – people were shocked and so concerned.”
She added: “Now thoughts are with the family and friends of the deceased and, of course, the wider community.”
Ms Kerley said the news was “devastating” for those will live in the “quiet, peaceful, lovely area”.
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