Two Department of Justice officials have been recalled to the Disclosures Tribunal and will give evidence again this week.
The tribunal is examining whether or not former garda commissioner Nóirín O'Sullivan inappropriately relied on unjustified grounds to discredit Sergeant Maurice McCabe at the O'Higgins Commission, a private inquiry set up in 2015.
Former secretary general Noel Waters and former deputy secretary general Ken O'Leary will be questioned again on Thursday.
They are being recalled in light of some of the evidence given by former minister for justice Frances Fitzgerald.
Another witness, Chief Superintendent Tony McLoughlin, has also been added for Thursday.
The tribunal has heard that there is a dispute between him and the force’s head of HR, John Barrett, over when Supt McLoughlin was told of an alleged comment by Cyril Dunne, the former garda head of administration.
Mr Dunne has denied making the remark.