A swimming ban is in place at four beaches in Co Galway. 

"Do Not Swim" notices have been placed at Silver Strand, Salthill, Blackrock and Grattan Road beaches. 

Galway City Council said the measure has been implemented as a result of very high levels of intestinal enterococci bacteria being found during routine testing. 

Swimming in the affected water can cause illness. 

The City Council is investigating to determine the cause of the pollution. 

The swimming ban may be in place until Saturday.