Published Wednesday, 07 November 2012
A forensic officer at the scene of the discovery in Portlaoise. (© PA)
He is being detained at Portlaoise Garda Station under Section 4 of the Criminal Justice Act 1984.
The arrest came after police searching for 30-year-old Aoife Phelan discovered a female body in Portlaoise on Wednesday morning.
Ms Phelan, who is from Cashel, near Portlaoise, was last seen on Thursday, 25 October.
The young woman, who was four months pregnant, was in work until 6.15pm on the day she disappeared.
She was employed as a live in au pair at The Hermitage in the town.
Ms Phelan met a friend at the Borris Road roundabout in Portlaoise at about 6.30pm and was last seen on 8.10pm when she left a friend's house at Colliers View.
On Wednesday at 11am, gardaí discovered a body while carrying out a planned search in the garden of a house at Timahoe Road in the town.
Forensic experts using a mini-digger and shovels had been excavating ground at the rear of the property.
A gardaí statement said: "The scene has been preserved, pending a full technical examination which has now commenced. The Office of the State Pathologist has been notified."
Preliminary examinations are being carried out by the State Pathologist Dr Marie Cassidy.
A post mortem will take place later on Wednesday.
Police divers were also examining a river bed about 12 miles away amid fears Ms Phelan's body had been thrown in to the River Barrow from the M7 on the Laois/Kildare border.
Meanwhile, a man in his 20s, from Portlaoise, arrested by gardaí on Monday was released without charge on Tuesday night.