Staff at St Conal's health campus in Letterkenny have been warned not to drink the water there.
Senator Pádraig Mac Lochlainn raised the issue yesterday.
He said staff there were told to drink bottled water as boiling would not solve the contamination problem.
“Staff are understandably very concerned” and “want to know the effects, if any, on the health of anyone who has been drinking the water”, he added.
In response to a query from the DD/DPP, an HSE spokesperson confirmed that a notice had been issued to staff advising them not to drink the water.
“We are taking advice from our public health specialist and the situation is under ongoing review,” the spokesperson added.