Irish Water has issued a 'Do Not Consume Notice' in Co Cavan affecting almost 8,000 customers.
The alert was published today for consumers on the Bailieborough Public Water Supply Scheme due to high levels of the mineral manganese.
It applies to 7,785 customers, many of whom are households and businesses, meaning tens of thousands will actually be affected.
The areas affected are Bailieborough, Killinkere, Virginia, Crossbane and Mullagh.
The caution is another step up from a Boil Water Notice.
A statement on the Irish Water website reads: "Following consultation with the Health Service Executive (HSE), Irish Water, working in partnership with Cavan County Council, has issued a 'Do Not Consume Notice' for all consumers on the Bailieborough Public Water Supply Scheme due to elevated levels of manganese in the water supply.
"The notice applies to 7,785 customers served by the Bailieborough Public Water Supply including Bailieborough, Killinkere, Virginia, Crossbane and Mullagh. Please note this is not a Boil Water Notice.
"Boiling the water will not reduce manganese levels and is therefore not a suitable measure to make the water safe to consume. It is especially important that mains drinking water is not given to bottle fed infants.
"This notice does not apply to other areas and water schemes in County Cavan."
For more information please visit the Irish Water website.
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