The historic Boyle mansion, King House, and Boyle Library have been closed after a big oil spill, caused by criminality.
Roscommon County Council, which owns the property, said: "Following recent criminal incidents in the grounds of King House, a significant spill of kerosene has taken place at the site.
"Roscommon County Council has engaged the services of specialist environmental contractors.
"To protect staff, visitors and collections, and to facilitate remediation works, all public events scheduled for King House and Boyle Library have been postponed and both locations remain closed until further notice."
The council says the matter has been referred to the gardai.
The council added: "Gardaí are also reviewing available CCTV footage as part of their inquiries. Roscommon County Council will fully support and cooperate with this investigation."
