Limerick City and County Council are cleaning the Treaty Stone after it was vandalised with blue paint overnight.
Council cleaning crews, along with staff from Limerick Civic Trust have been at the site since early this morning.
A water based paint possibly art paint from a tube was daubed all over the monument. From initial investigation there is no lasting damage.
Street cleansing crews are power hosing down the monument. It appears the damp weather last night meant the paint didn't adhere to the Stone.
A specialist will examine the Stone as a precaution. Gardaí at Henry Street are investigating and are viewing CCTV footage of the area. They can be contacted on 061 212400.
Mayor of the City and County of Limerick, Cllr Kieran O’Hanlon condemned the act: “This is mindless, wanton thuggery. Who would want to deface any property? Let alone one of the iconic symbols of Limerick. Whoever did this should be ashamed of themselves. Their actions impact on everyone, on Limerick and I would encourage anyone who saw anything or knows who did it to contact the gardaí. These types of actions have got to be stamped out.”