About 25 demonstrators stormed the Nelson City Council offices on Thursday morning in protest at proposed Three Water reforms.
It's understood they made it as far as the foyer of the building just before 9am, but have since been kicked out.
Nelson City Council chief executive Pat Dougherty says the protesters had put staff at risk by "not physically distancing and not wearing masks".
As a result, a decision was made to temporarily close the doors of the council building to prevent more demonstrators from entering.
The incident comes as councillors meet on Thursday to discuss the reforms and provide feedback to the Government.
Dougherty says he'd already given Three Waters critics an opportunity to voice their opinions.
"A representative of the group was already included on the list of public speakers for today's meeting. There were several other public speakers that took the opportunity to address the meeting via Zoom," he explained.
“I received their petition, and that was presented as part of the council meeting, but I urge the public to remember that under Delta Alert Level 2, we have strict limits on the numbers of people that can be in our Customer Service Centre and our Council Chamber."
A police spokesperson told Newshub they were aware of a protest outside the council building, but said no one involved had been arrested.
"Police recognise and respect the lawful right to protest, however we must also ensure the safety and well being of our community," they said.
"In this case, Police are on site to ensure the safety of all involved. No arrests have been made at this time."
More than 100 people have turned up to the protest, many of them brandishing signs in opposition to the Three Waters reforms.
"Nelson's water supply is not for sale," read one, while other demonstrators held signs demanding the Government have a referendum on the issue. "Democracy not dictatorship," read another.
It comes as the Government proposes the establishment of four publicly-owned entities to take responsibility for drinking water, wastewater and stormwater infrastructure to stop average household bills reaching $9000 by 2051.
A report by the Water Industry Commission for Scotland estimates that New Zealand will need to invest between $120 billion to $185 billion on water infrastructure over the next 30 years to meet standards and provide for future population growth.
Local Government Minister Nanaia Mahuta says the proposed reforms are not only necessary, but will also grow GDP by $14 billion to $23 billion over the next 30 years and generate 5850 to 9260 full-time equivalent jobs.