Galway County Council has confirmed that the water supply in the Athenry town has been contaminated by farmyard waste.
Tests carried out this week indicated bacteriological contamination.
The effluent leaked into the town’s water source during heavy rainfall last week.
The Council are currently providing emergency drinking water supplies for around 3,000 people.
This is available from two storage tanks, located in front of the Public Library and in the car park opposite Cloonan's garage.
There were similar recent water contamination alerts in the region, with Ballinasloe being affected last August and Galway City last June.
Galway County Council also said the Tuam Regional Water Supply Scheme extension to Athenry Town, which will supply water from Lough Corrib to the town, is expected to be in operation by early next month.
