Gardai are searching a wooded area in Chapelizod in South Dublin as part of the investigation into the disappearance of Trevor Deely.
The 22 year old from Co Kildare was last seen over 17 years ago close to Baggot Street Bridge in Dublin.
Gardai say the search is being carried out after new information came to light and it will take several weeks.
Gardaí have been searching since early this morning and will bring journalists to the site after a press conference this lunchtime.
In April detectives carried out a complete review of the case and gathered more detailed information from enhanced CCTV footage.
They released the footage appealing for a man dressed in black and seen talking to Mr Deely to come forward.
The Deely family has been informed of today’s developments.