A man has been arrested on suspicion of murder over the disappearance of a Belfast woman last year.
Saoirse Smyth, 28, was last seen in April 2017 in the Belfast area.
The PSNI announced on Thursday that a murder investigation has been launched into her disappearance.
Detectives arrested a 40-year-old man on suspicion of Ms Smyth’s murder in the Newry area on Wednesday evening.
He remains in police custody at Musgrave Serious Crime Suite, and is being questioned.
Ms Smyth’s family have urged anyone who can help the police to find out what happened to her to come forward.
“Somebody out there must know something about what has happened to Saoirse and we would plead with anyone who knows anything to contact the police - and Saoirse, if you are out there, please contact your family and let us know you are okay,” the family said in a statement.
A missing person appeal was launched for Ms Smyth last December.
She is described as having very distinctive red hair.
Although Ms Smyth was last seen in the Belfast area in April 2017, her last known movements at that time can be traced across the Irish border to Omeath, Co Louth, where she was living.
An address in Omeath was searched on Thursday in connection with Ms Smyth’s disappearance.
Detective Chief Inspector Geoff Boyce said he believes she was murdered.
“The investigation into Saoirse’s disappearance has progressed, and while keeping an open mind I now believe that the potential exists for Saoirse to have sadly been murdered,” he said.
“Saoirse was seen in the Belfast area in April 2017. She had very distinctive red hair and has not had any contact with her family or friends during this period, including on significant dates such as her birthday and Christmas, and this is very unusual.
“Saoirse also hasn’t responded to any of her family’s pleas on social media. This, along with other information obtained during the police investigation now leads me to believe that Saoirse may have been murdered.”
Mr Boyce said because Ms Smyth’s last movements can be traced to Omeath, the PSNI are working with their Irish colleagues in An Garda Siochana on the investigation.
He has appealed to anyone with information that may help detectives to come forward.
“Her family deserve to know what has happened to her,” he said.
“I have been in contact with her family who understandably have been left devastated and trained Police Family Liaison Officers are supporting the family at this very difficult time.
“I am particularly interested in speaking with anyone who has seen Saoirse or who has contact with her since January 2017.
“Anyone with information about her disappearance should contact detectives at the incident room Ladas Drive on 101, or +4428 9065 0222 if you are calling from RoI.”