The chairman of GSoc Simon O Brien has said he is focusing on an internal mole within his organisation - but said he "cannot rule out" the possibility that it could have been a member of the Garda Siochana.
Mr O Brien admitted it was an "unpalatable possibility" to hear that he had to include this possibility of garda involvement in a potential list of suspects.
He also admitted that it was probable that further leaks from the secret report will come out in the same Sunday newspaper which published details of a breach of security at his office.
Mr O Brien said seven people knew of the contents of the secret report while ten knew that a "sweep" was being done of their office by a team of UK experts.
An internal investigation is being carried out within GSOC to find out who was responsible, he told members of a Joint Committee on Oversight.