The man in his 60s who was arrested on Thursday morning on suspicion of the murder of Annie McCarrick in March 1993 has been released without charge.
He was previously detained under Section 4 of the Criminal Justice Act 1984.
Gardaí are continuing to investigate Ms McCarrick's disappearance and murder.
The searches in relation to the investigation are ongoing and being supported by a cadaver dog from an external agency, a garda statement said.
Searches will continue over the weekend, and updates will be provided as appropriate, it added.
Investigations are ongoing.
