Detectives were yesterday questioning a man about the murder of a shop assistant who vanished from a caravan site party in Co Down.
No trace has been found of 25-year-old Lisa Dorrian's body, despite air, land and sea searches. She disappeared from Ballyhalbert caravan site near her home in Bangor, Co Down, last February.
Loyalist paramilitaries have been blamed for the murder.
Her family has campaigned relentlessly in an attempt to keep public attention focused on the case.
The Irish Government and British prime minister Tony Blair have both pledged support in helping to find Ms Dorrian's body.
Detectives have already questioned and released four men about the killing.
A Police Service of Northern Ireland spokesman confirmed yesterday a 22-year-old man had been arrested in connection with the investigation.
It is thought that a scientist being brought in to help find the remains of five people murdered and secretly buried by the IRA during the Troubles may have his remit extended to include Ms Dorrian.
Her family had previously offered a reward of £10,000 for information leading to the recovery of her body.