He's being detained at a garda station in the east of the country.
Another man has been arrested in relation to the murder of Ashing Murphy.
Aged in his 30s, he's being detained at a garda station in the east of the country.
He's being questioned in relation to potential withholding of information contrary to The Offences Against the State (Amendment) Act 1998, and is being held under the provisions of Section 30 Offences Against the State Act 1939 as amended.
Another man in his 30s remains in custody in Tullamore Garda Station today.
He was arrested in Dublin yesterday.
Gardaí can continue to question the individual under the provisions of Section 4 of the Criminal Justice Act 1984 until later this evening, after which they will have to either charge or release him.
Today marks a week since the 23 year old was killed while out for a run along the Grand Canal in Tullamore.
A public appeal for information remains, including about a man in a black tracksuit and runners who's believed to have been in the Grand Canal area in Tullamore around the time of Ashling's death at 4pm last Wednesday, 12th January.
Gardaí remain at the scene today, but are offering no further information at this time.