Gardaí are continuing to question a man about the death of Paiche Onyemachi (25) last month.
The man, who is Nigerian, is being held at Bridewell Garda station in Dublin and can be detained until tomorrow evening under Section 30 of the Offences Against the State Act.
A second Nigerian man was released without charge yesterday evening.
The headless body of Ms Onyemachi, the daughter of the Chief Justice of Malawi, was discovered in a black plastic bag near a river in Piltown, Co Kilkenny, on July 23rd.
The mother-of-two had been missing from her Waterford home for three weeks.
The two men were arrested in the O'Connell Street and Parnell Street areas of Dublin yesterday afternoon.
Gardai said they would also like to speak to the victim's husband, Chika Onyemachi (31), who did not attend her funeral and has not been seen since.