A 24-year-old man is still being questioned this morning over the disappearance and murder of Aoife Phelan from Co Laois.
He was detained just hours after a woman's body was found yesterday, close to where Aoife was last seen.
He is being questioned at Portlaoise Garda Station under Section 4 of the Criminal Justice Act and can be detained for up to 24 hours.
A 24-year-old man was also arrested earlier this week before being released on Tuesday night.