Monday's search is on an area of open ground, after the scene was prepared for the search in recent days.

The disappearances of both women are being treated as murder investigations by gardaí.

Deirdre Jacob disappeared from near the front gates of her parents’ home in Roseberry, Newbridge, Co Kildare on the afternoon of July 28 1998. She was 18 at the time.

21-year-old Jo Jo was last heard from when she made a phone call to her friend, Mary Cullinan, from a phone box in Moone, Co Kildare, at 11.37pm on November 9, 1995.

She was on her way home from Dublin, where she had enjoyed socialising in Bruxelles Bar, Harry Street, Dublin 2. She had left home in Callan at 8.30am that morning and had hoped to get a bus back home to Kilkenny that night, but missed it.

She managed to get another lift to Moone, Co Kildare, at around 11.15pm, from where she made the last phone call to Mary Cullinan.

She cut the phone call short and told Mary that a car had stopped and she was going to take the lift. No further sighting was made of Jo Jo after that.

In a Garda statement on Monday, gardaí said: “Gardaí were assisted by the Defence Forces last week, under Aid to Civil Power arrangements in completing a technical ground survey of an area in Co. Wicklow, near the Wicklow/Kildare border. 

"This area of land will now be searched and subject to excavation and forensic examinations over the coming days.” 

It continued: “The search operation is being led by the Serious Crime Review Team, Garda National Bureau of Criminal Investigation in conjunction with Gardaí from the Kildare/Carlow Division and is supported by the Garda National Technical Bureau and the Wicklow Garda Division. An Garda Síochána has been and continues to keep the families of Jo Jo Dullard and Deirdre Jacob updated in relation to these investigations and they have been fully appraised of these developments.” 

Gardaí have appealed to anyone with information no matter how small it may seem, to contact Kildare Garda station on 045 527 730 or any Garda station, or anyone who wishes to provide information confidentially should contact the Garda Confidential Line on 1800 666 111.