The head of Irish Water has said there is a possibility of more boil water notices in the weeks and months ahead.
More than 600,000 people in Dublin, Kildare and Meath served by the Leixlip Water Treatment Plant are currently forced to boil their drinking water.
Testing at the plant is continuing, after large amounts of organic matter was washed into reservoirs, increasing the turbidity - or 'cloudiness' - of the source water above acceptable levels.
The Environmental Protection Agency is set to carry out an audit at the plant today.
It is believed that recent heavy rain has caused further problems, and it is still not certain when the current notice will be lifted.
And Irish Water’s Managing Director Niall Gleeson said he could not rule out more alerts being issued in the coming months.
He told Morning Ireland on RTE Radio One: "Given the condition of the plant and what we're seeing now there is a possibility of another boil water notice.
"But as I say we have our engineers on site, we are looking at getting the plant back in service this week but we're also looking at the longer term.
"If we can add functionality to the plant so we can help it ride through these storms, and then bring it back online when these storms have passed, pumping up the reservoirs and maximising the other plants.
"So we're doing everything we can to give more confidence around the plant. But I can't rule out another boil water notice."
Mr Gleeson was also unable to confirm when the current notice affecting over half a million customers would be lifted.
He added: "I would like to apologise personally, it's a major inconvenience.
"Today we have the EPA on site with the HSE, our own engineers and Fingal engineers are on site as well.
"We've made quite a few improvements to the plant during the week and it's operating well.
"We have taken a lot of data of how the plant is operated this week, and that's what the EPA will be looking at, along with the two satisfactory samples that we have from the water that is entering the system.
"Right now the plant is delivering the water to the quality that we need, but the EPA and the HSE will need to see that we can consistently deliver that quality, and they will need to look at historical records of how the plant is performing during the week."
