A County Tyrone man has been arrested in connection with the 1998 Omagh bomb.
Twenty nine people died in the Real IRA attack
Detectives from Dungannon arrested the 44-year-old on Wednesday.
He is being questioned about serious terrorist crime linked to the bomb.
Twenty-nine men, women and children died and hundreds were injured in the car bomb attack in the County Tyrone town on 15 August 1998.
It was the single worst atrocity in 30 years of violence in Northern Ireland.
To date, only one person, Colm Murphy, has been jailed for having a role in the bomb. In January 2002 the Special Criminal Court in Dublin sentenced the Dundalk-based builder and publican to 14 years in jail.
Murphy and four others; Seamus Daly, Seamus McKenna, Michael McKevitt, and Liam Campbell are being sued by the Omagh Victims Civil Action Group.