Bathing restrictions are in place on three popular beaches in Dublin.
Dún Laoghaire-Rathdown County Council has issued a restriction notice banning swimming at Killiney and White Rock beaches.
It follows the results of samples taken on Monday, which showed high levels of E Coli and Enterococci contaminants.
An investigation is under way into the cause of the contamination.
There is also a temporary ban on bathing at Sandymount Strand, one of Dublin's most popular beaches.
Dublin City Council said that water samples did not comply with quality standards set down.
The local authority said the ban will be in place until at least tomorrow, when further tests will become available.
Dublin City Council said bathing waters can be temporarily impacted by weather and tidal conditions, faecal matter from dogs and birds and temporary overflows from drains.