Gardaí sealed off a Cork forest and began a massive search operation after a phone call led to a tip that a person matching the description of missing Tina Satchwell (45) was seen in the vicinity of the woods last year.
The caller told gardaí the person matching Ms Satchwell's description was spotted near Mitchell's Wood, outside Castlemartyr, in east Cork, last March.
She was apparently accompanied by someone at the time.
The caller saw a blonde-haired woman near the woods - but did not see her subsequently leave the area.
Gardaí received the call in the wake of an RTÉ 'Prime Time' report on the case in January.
Detectives refused to comment on the tip-off that sparked the huge search operation, which yesterday resulted in 100 metres of steel security fencing being erected across the entrance to Mitchell's Wood, just metres from the luxurious Castlemartyr Resort.
The security fencing was later clad with plastic sheeting to allow search teams to operate away from the public gaze.
Superintendent Colm Noonan, of Midleton garda station, issued a public appeal for information as the massive search operation began for Ms Satchwell, who vanished without trace on March 20, 2017.
The operation is backed by 60 search personnel and involved an entire section of the woodland being cordoned off.
Massive generators were delivered to the scene, together with outdoor lighting systems.
Portacabins, a special Garda communications vehicle and portable toilets were delivered to the search site.
A team from Search Dogs UK is also helping the Garda operation, as well as Defence Forces' engineering units.
More than 40 acres will be examined in an operation expected to last three weeks.
"Gardaí at Midleton are investigating the disappearance of Tina Satchwell, from Youghal, who was last seen in March 2017," Supt Noonan said.
"There have been 220 separate lines of inquiry conducted. This has included liaison with Interpol and we are now conducting a search at Mitchell's Wood.
"We are looking for evidence in relation to Tina's disappearance and we have, for the purposes of this search, restricted access to this area.
"I would appeal to members of the public to stay away from the area - there will be no public access for the duration of this search."
Supt Noonan confirmed they have all necessary equipment and support for the search of the sprawling woodland. A specific 40-acre section has been identified in the 200 acre woodland as the focus of the search.
"Particularly, I wish to urge anyone who has information relating to activity in or around Mitchell's Wood, Bridgetown, Castlemartyr, Cork, at the time of Tina's disappearance in March 2017 to contact the incident room at Midleton garda station."
Supt Noonan refused to comment on what specific information gardaí had obtained or why Mitchell's Wood was being targeted. However, the information was received over recent weeks and involved the movement of specific individuals in the vicinity of the forest.
One Garda source said the information was believed to be "credible and reliable".
Supt Noonan said Ms Satchwell's family were being fully briefed on the operation.
"We are in regular contact with the family and they have been informed of this search operation today.
"You will appreciate that this is a very stressful time for them and I would urge that they be afforded privacy at this time."
The searches represent the first major operation undertaken outside the greater Youghal area where Ms Satchwell was last seen.
A property was searched by gardaí in the east Cork seaside town last year - and underwater searches were also conducted by divers in Youghal Bay.
However, no trace of Ms Satchwell has been found.
The first anniversary of her disappearance is in two weeks' time. The searches were planned for the Castlemartyr woodland for late February but had to be rescheduled because of Storm Emma.
Ms Satchwell's husband, Richard, is adamant she left home to deal with personal issues.