The Dublin City Returning Officer said he has notified gardaí about the potential breach of the election laws.
The image and name of a bye-election candidate in Dublin Central was marked on pavements outside a number of polling stations in Dublin using a power hose.
Joe Burke said that when the issue was brought to his attention he notified gardaí, Dublin City Council and the candidate themselves.
He said that it was the first time, in his role presiding over elections in the capital, that he had seen something of this nature occur.
An Garda Síochána said electoral legislation provides for "specific offences in proximity to polling stations and count centres".
It said gardaí have received reports of a "number of occurrences in north Dublin today, adding that "enquiries are ongoing".
A spokesperson said the "protection of the electoral process" is a priority for gardaí and "central to democracy".
They said a garda presence will remain in place in the DMR North, DMR North Central and DMR West Divisions until polling closes at 10pm to ensure voters can "exercise their democratic right without interference".
Dublin City Council said it will be issuing fines to a bye-election candidate in Dublin Central after their image and name was marked on pavements outside a number of polling stations in Dublin using a power hose.
The technique, which leaves a mark on concrete by using stencils and power washing machinery to bring up words and images that are cleaner than the rest of the pavement, was deployed in several locations around Dublin Central before being reported to the council.
Dublin City Council said the practice is in breach of both litter legislation and electoral legislation which restricts the distance that candidates material can be displayed from a polling station.
The council said it will be issuing fines to the candidate and that it has deployed a number of cleaning crews to try and remove the imagery from the polling stations.
Follow live: Voting under way in Galway West and Dublin Central
