Dirty water in the vicinity of Parliament House and the Parliamentary Library in Wellington triggered a warning to staff not to drink tap water.
An email sent out earlier today advised not to drink it as a "precautionary measure" because of an external issue.
"The Buildings and Safety team is investigating with Wellington City Council. The team will provide an update when the water is suitable for drinking again."
But there was no reason provided for the sudden warning.
Wellington Water's drinking water chief adviser Laurence Edwards has since confirmed they responded to reports of dirty water being experienced in the buildings at about 11.30am.