A fresh search has begun for the body of Arlene Arkinson, the Castlederg teenager who disappeared more than 20 years ago after attending a disco in Bundoran.
The new searches are on farmland at Killen, around a mile from Castlederg, close to where Arlene was last seen.
The PSNI operation was launched after a report of some disturbed earth.
The 15-year-old disappeared in August 1994 and was last seen being driven down a country road late at night by Robert Howard.
He was acquitted of the murder in 2005. The jury were not told that he had been convicted in 2003 of the 1999 rape and murder of teenager Hannah Williams in south London in 1999. Howard died prison last year.
PSNI Det Chief Supt Raymond Murray said: “The family of Arlene Arkinson have been advised of this development purely as a precautionary measure.
“It would be premature to draw any inference from this initial report or the police response to it at this time.”