A teenager was arrested yesterday afternoon following a break-in at Leinster House.
The 16-year-old boy managed to get access to the building and it is understood some damage was caused.
Gardaí said the "incident of trespass" happened at around 4pm.
It is understood that the boy gained access to the campus from the Merrion Street side.
Officers from Pearse Street Garda Station arrested the boy and he was questioned at a garda station in the city.
He has since been released without charge and a file is being prepared for the Garda Youth Diversion Programme.
A spokesperson for the House of the Oireachtas said that it does not comment on security matters.
Military Police are present on the campus during non-opening days.
Social Democrats TD Jennifer Whitmore, a member of the Oireachtas Commission that oversees the running of Leinster House, described the intrusion as "worrying", adding that "it's important that security is examined and any gaps are identified and rectified quickly".
The Cathaoirleach of the Seanad, Senator Jerry Buttimer, described the break-in as "a very serious breach of security that must be investigated".
Senator Buttimer said that the matter will be discussed at the next meeting of the Oireachtas Commission.
"Thankfully, the gardaí apprehended the intruder," said Mr Buttimer, adding it is "concerning the person was able to gain access" to the house.
Additional reporting: Tommy Meskill