Gardaí investigating the disappearance of Trevor Deely almost 17 years ago were carring out excavation works at a site in Dublin on Monday.
Mr Deely disappeared after a Christmas night out with work colleagues in Dublin.
A number of gardaí were on site in Chapelizod on Monday as heavy digging equipment arrived. Officers were also observed placing black sacks into a van which had arrived at the scene.
The initial search commenced on Saturday after detectives in the case received new information regarding the disappearance of Mr Deely. The three-acre woodland site was cleared over the weekend.
"Excavation works are continuing at the site this morning but this is very early days in our investigation. This search could last a number of weeks as there is a wide area to cover," a senior Garda source told The Irish Times.
“We are dealing with a three-acre site and dense undergrowth. We have installed CCTV cameras to cover the perimeter of the area we are searching.”
It is understood gardaí are trying to establish a location on the site which is of particular interest to investigation gardaí.
The search for Mr Deely has zoned in on the wasteland after gardaí investigating his disappearance received intelligence suggesting he was murdered by a known criminal.
“This is the biggest lead we have had in this case so far over the years. It’s early days but are hopeful that this investigation might help us establish what happened to young Trevor,” said the senior Garda source.
The investigating team is also treating as credible information claiming to know the exact spot where Mr Deely’s body is buried.
The criminal, and others close to him, was involved in the drugs trade and other serious crime.
Mr Deely, who was 22 and working for Bank of Ireland when he vanished on his way home from an office party in the early hours of December 8th, 2000, was not known to the people gardaí suspect killed him and concealed his body.
The search of the new site owned by South Dublin County Council was sparked by a "significant" tip-off.
It is understood the source of the latest development is not the same individual who was captured on CCTV speaking to Trevor on the corner of Baggot Street and Haddington Road.
The footage formed part of an appeal in April after which led to gardaí receiving hundreds of calls.
Minutes after that conversation Mr Deely was captured on CCTV walking towards Haddington Road with what gardaí believe to be the same man 20 yards behind.
A new cold case team was set up last December to carry out a complete review of Trevor’s disappearance.