Detectives checked a room for bugs when civil servants met there to choose the winner of the second mobile phone licence.
The electronic sweep of the room in the Department of Communications in Dublin's Kildare Street followed fears in 1995 that the confidentiality of the process could be breached.
The revelation emerged from a document mentioned at the Moriarty Tribunal in Dublin Castle yesterday, where a Danish consultant was giving evidence.
Prof Michael Andersen, a key consultant to the award of the second mobile phone licence, was giving evidence for the fourth day.
Michael McDowell SC asked Prof Andersen, the project leader of the team choosing the winner of the competition, about a meeting in September 1995.
Prof Andersen said he had no recollection of a meeting, but said that did not mean it did not happen.
Two Irish public servants have given evidence of attending a meeting with Prof Andersen when the weightings of the competitors' bids were changed.
Prof Andersen complained about having to repeat his explanations of how the licence competition operated back in 1995. "We've been over this a hundred times," he said.
The tribunal will sit from 10am to 5pm next week to facilitate Prof Andersen, the final witness, finishing giving his evidence by next Friday.