Kerosene has been found in the water supply of around 75 houses in Galway.
The homes in the Moyola estate were advised yesterday to stop using the public supply.
It is understood that the water has been affected for the past week.
Residents are urged not to use water from taps for drinking, preparing food, brushing teeth, making ice or bathing.
Water from the tankers dispatched by the Council must still be boiled before use.