Forensic experts have carried out a detailed examination of a derelict flat once occupied by a man cleared of murdering a missing schoolgirl from Co Tyrone.
Officers in white boiler suits moved into the property in the centre of Castlederg, where child killer Robert Howard lived at the time of Arlene Arkinson's disappearance 18 years ago.
The flat in Main Street in Castlederg has been searched before but a forensic team was called in after serious crime branch detectives got new information.
Body recovery dogs were also brought in to help a search team check land between Castlederg and the village of Clady on the Tyrone-Donegal border.
15-year-old Arlene, vanished on her way home from a disco in Bundoran, in August 1994. It's believed she had been seen with Howard who was acquitted of her murder in 2005 when he was aged 61.
He is currently serving a life sentence for the rape and murder of 14-year-old schoolgirl Hanna Williams, from Deptford, south London, whose body was found in a cement works in Northfleet, Kent, in March 2002.
The flat where Howard lived when Arlene disappeared has been derelict for some time and officers had to make sure it was safe to enter before todays detailed forensic examination got under way.
The PSNI have said that the Arkinson family had been kept up to date about the progress of the investigation.