GARDAI will today begin an intensive search of woodland outside Portlaoise for the body of missing Fiona Pender.
Ms Pender disappeared without a trace almost 20 years ago, but this is to be the most extensive search carried out to date after they received "significant" information.
The Offaly hairdresser, who was seven months pregnant, was presumed to have been murdered shortly after her disappearance in 1996.
The specialised forensic search was ordered after a female witness came forward to gardai with "credible information" about a specific location where Ms Pender may have been buried.
This witness is the former partner of the man gardai believe is the prime suspect for the murder of the 25-year-old.
It is understood that the woman broke her silence after her life was threatened by the prime suspect in another jurisdiction.
She has since met with gardai from the Laois/Offaly division, who interviewed her at length over recent months.
It is understood that the woman, who is in protective care abroad, pointed out an area of woodland outside Portlaoise. She has told detectives that the prime suspect brought her to this area on a number of previous occasions when they were home on holiday and allegedly told her he buried Ms Pender there.
He also threatened her life and told her that the same thing would happen to her if she ever crossed him.
The search operation, which is under the command of Chief Superintendent John Scanlan, is expected to last for anything between two and six weeks.
A small team of specialist officers will use the latest technological equipment as well as cadaver dogs brought in from the UK that are trained in the recovery of skeletal remains.
A forensic archaeologist will also be on hand.
A source said last night: "This will be a highly specialised forensic search which will continue effectively for as long as it takes - the information is very significant and the first really concrete lead in the case of Ms Pender's disappearance.
"The gardai in Tullamore have never given up on this investigation, and because of the nature of the information we have, it will be a slow, methodical search that will go on for weeks."
Ms Pender, who was also a part-time model, was last seen alive at Church Street, Tullamore, Co Offaly, on the morning of August 23, 1996.
Gardai have always believed that she was murdered by a man known to her.