An emergency water supply being provided for residents in the Old Mervue area of Galway city has had to be suspended because high levels of lead were found in it overnight.
Residentshave expressed shock that an emergency supply, laid on four days ago, has now also been found to be unsafe to use.
It had been claimed that the contamination problem was caused by old lead pipes but the emergency supply had come from a cast iron water main.
The city council says it is disappointed at this latest development and is making arrangements to provide an alternative supply for containers.
The Mayor of Galway, Pádraig Conneely, says the situation is appalling and totally unacceptable.
The street taps at the centre of this latest scare were installed on Wednesday and the Corporation assured the 1000 residents who live in Old Mervue that the water was safe to drink.
Last night however one of two tests carried out on the water showed that it contained over four times the acceptable level of lead.
The council says it immediately suspended this emergency service and is awaiting the result of further analysis which will be available on Monday.
In the meantime it is arranging to have safe drinking water provided from containers which will be located around the estate.
A spokesman for the council said it was disappointed with the result of the test and it apologised to the residents.
But mayor Pádraig Connelly said he was shocked by the news.
He said it was now time for Environment Minister John Gormley to come to Galway and appoint a senior official from his department to take charge of the city's water services.
He said the most worrying thing was the effect drinking the water might have had on residents this week.
Meanwhile, Cork Council Council has announced that it is to replace a mains lead pipe which supplies water to 56 houses on Beecher Street in Mallow.
Yesterday, the council revealed that tests in houses on the street showed up to three times the permitted levels of lead in the water.
Councillors in angry meeting
Councillors in Galway met for almost five hours last night to discuss lead contamination in part of the city's water supply.
They were told that short and long term solutions were being examined in an effort to resolve the issue.
But the city's mayor said not enough was being done to restore public confidence.
There were heated exchanges at last night's meeting between officials and elected representatives, with Cllr Conneely describing an action plan to deal with the latest problem as pathetic.
Council officials says they are doing all they can to resolve the issue and that a number of potential solutions are being looked at.
These include an adjustment of ph levels in the water, additional treatment measures and - eventually - the replacement of a lead distribution pipe in the Old Mervue part of the city.
However, this could take up to two years to complete.
In the meantime, residents in the areas affected by the contamination will meet council officials over the next fortnight and bottled water is to be subsidised in local shops, with free supplies being delivered to elderly people.