Two investigations are under way after an intruder accosted the president in Áras an Uachtaráin last week.
A woman allegedly drove through the front gate of the presidential residence, walked in the front door and spoke to President Michael D Higgins in his office on Friday 14 September.
President Higgins was not attacked or assaulted and gardaí arrived a short time later and escorted the woman away.
The woman, who is in her 50s, was not arrested and was allowed drive out of the Áras.
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Garda Headquarters has said it does not comment on security matters, but confirmed that a senior officer is investigating the incident.
A review of security at Áras an Uachtaráin is also being carried out by another officer.
President Higgins is to be interviewed, along with gardaí and staff at the Áras.
When questioned about the incident, which was first reported in the Irish Daily Mail, the President's press office said they would not be commenting on security matters.
Investigations are underway following a security breach at Áras an Uachtaráin. A woman gained access to the building and accosted President Higgins on 14 September pic.twitter.com/WPckzM1sYy— RTÉ News (@rtenews) September 22, 2018
Armed and uniformed gardaí, as well as Defence Forces personnel, are posted to the Áras but it is the gardaí that are responsible for security.
The Defence Forces carry out administrative roles on a daily basis such as organising drivers and the Aide de Comp.
The security breach is a major embarrassment and while there is relief in garda and Government circles that something more serious did not occur, it is expected that disciplinary proceedings will be instituted.