Gardai are liaising with police in Northern Ireland in a bid to find the whereabouts of a man they believe may have been seriously assaulted in Co Donegal.
Officers are desperate to contact the man's family in a bid to determine when he was last seen.
A search for the alleged victim, who is believed to be in his 60s, is still continuing in the Slieve League area of Donegal.
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The remote sea cliff location has been closed off by Gardai to visitors for the past three days.
Gardai will decide this evening if that search will continue tomorrow.
Two people arrested in connection with the investigation were released without charge on Tuesday evening.
The widespread search was sparked after a suspect in the case, a woman in her 20s, contacted a friend to say there had been a serious assault and identified the Slieve League area.
Gardai immediately launched an investigation and arrested the man and the woman suspected of being involved.
The man's car was seized and splatters of blood were found in the vehicle which are still being examined by officers.
A house in the Killybegs area was also sealed off and forensic officers also carried out an examination of the home.
A key part of the Garda investigation will centre around a recorded phonecall made by one of the suspects to the third party who later contacted Gardai.
While it is not understood that there were admissions made in the phonecall, it may well form part of the Director of Public Prosecution's case if anyone is charged with a crime.
Investigating Gardaí continue to appeal to any person who may have information in relation to this incident to contact them.
Garda sources say they specifically want to hear from anybody who noticed anything suspicious in the Killybegs, Kilcar or Slieve League area between Saturday afternoon and Sunday evening.
Anyone who may have camera footage (including dash cam) is asked to make this available to investigating Gardaí.
Anyone with information is asked to contact Ballyshannon Garda Station on 071 985 8530, the Garda Confidential Line on 1800 666 111, or any Garda station.
