Convicted child killer John Clifford, who murdered his young niece, is unlawfully at large after failing to return to Maghaberry Prison.
The 56-year-old, who uses a mobility scooter, was on day release to attend an appointment - but failed to return on Sunday evening.
Police and prison officers are working to track Clifford down, while the circumstances surrounding his how he managed to abscond are also being investigated.
A spokesperson for the Northern Ireland Prison Service said: “At this time, we are focused on returning him to custody and would ask anyone with information to contact the PSNI immediately.”
Clifford is described as being around 5ft 7ins tall and of medium build, with a fresh complexion, green eyes and fair hair.
When last seen, he was wearing a black beanie- style hat, a heavy black coat, grey trousers and black dress shoes.
He uses a distinctive three-wheel mobility scooter with the registration EXZ 4974.
PSNI Inspector Paul Noble said: “Anyone with information about his whereabouts should contact us immediately on 101.”
Clifford was jailed for life in 1989 for murder and a string of other offences, including indecent assault and cruelty to children.
He was released in 2005, but returned to prison two years later for breaching the terms of his probation.