The issue was detected in the Achill Public Supply Scheme causing the group water schemes in Slievemore, Doogort, Dooinver, Dooega and Saile to ceased operations according to the Western People.
All of the islands 2,400 residents were warned not to consume the water, with a particular warned extended to parents of infants being bottle-fed.
Following consultation with the HSE and Irish Water, Mayo County Council issued the notice, explaining the same rules do not apply as they would to a Boil notice.
The council explained: “Boiling the water will not reduce aluminium and turbidity levels and is therefore not a suitable measure to make the water safe to consume.”
The water remains safe to use for hand-washing and hygiene purposes.
On Friday evening, water tankers were put in place in five locations around the island, with a further 12 expected to be operational by this evening.
In a statement, Irish Water said: “We acknowledge the impact of this notice on the local community in Achill Island. We are working closely with our colleagues in Mayo County Council to lift the notice as quickly as it is safe to do so and safeguard the water supply for the future.”