Around €500,000 in damage has been caused to vehicles and facilities at a site used by the Office of Public Works to allow their staff to access Castletown House in Celbridge in Co Kildare.
Four vehicles were overturned, a construction vehicle was driven into a river, and wires on four CCTV units were cut on the lands of Donaghcumper House over the Bank Holiday weekend.
Castletown House and estate has been at the centre of an 18-month-long row between locals and the OPW about access to the heritage site.
Gardaí said they are investigating an incident of criminal damage at the site and their enquiries are ongoing.
In a statement, Minister of State with responsibility for the Office of Public Works, Kevin 'Boxer' Moran, described the incident as "shocking and unacceptable".
"This criminal damage to State property owned and managed by the OPW is shocking and unacceptable. A garda investigation is under way.
"The cost of the damage to the OPW will be in excess of €500,000. I would urge anyone with information to contact An Garda Síochána. At this time, the safety and well-being of OPW staff is of paramount importance."
The OPW said it already has significant security infrastructure in place at Donaghcumper and has added to this on the advice of An Garda Síochána.
It said that staff have been reporting to Donaghcumper House to be transported to Castletown House in OPW vehicles since they returned to work there on 10 April.
It says that between 22 April to 30 April, a number of incidents took place in the Donaghcumper House site, including fire damage to outbuildings and staff welfare facilities.
On Monday, Mr Moran made a renewed appeal to solve the stand-off, which has seen locals keep a presence at the entrance to the site and OPW staff not attending for work there for most of the past year.
