Galway City Council has advised against sea swimming in Salthill until further notice, after high levels of a bacteria were detected in the water.
The "elevated" levels of intestinal enterococci, which can cause gastro-intestinal illness, were detected at the Blackrock and Ladies' beaches in Salthill in samples taken on Monday. Full results became available on Thursday, it said.
The city council said the cause was unknown and investigations were continuing.
Galway has been the only Irish city to enjoy blue flag beach status in recent years, mainly due to its population size and the impact of the Mutton Island sewage treatment plant.
The local authority said it posted “do not swim” notices at both beaches on Thursday afternoon following advice from the HSE.
Testing for intestinal enterococci is one of two new microbiological parameters which have been monitored by local authorities since 2011 on advice from the Environmental Protection Agency.
The city council said that results of re-sampling would be available on Saturday. It said samples taken from Grattan Road beach and Silver Strand nearby were “well within guidelines for safe swimming”.
