The 22 year old, from Naas, was last seen in December 2000 walking home from his Christmas Party close to Baggot Street Bridge.
Gardai in Dublin say that they might be weeks searching a on three acres of woodland which has been sealed off in Chapelizod in south Dublin.
It is understood that the source chose to provide the information after being interviewed during a "cold case review" of the original investigation.
Detectives believe he was the same man who was seen on CCTV following Mr Deely a short time later on Haddington Road.
Despite an appeal last April for the man to come forward, he still has not been identified.
The file on Trevor Deely has never been closed and there have been a number of appeals for information over the years but Trevor has never been found.