Parts of Lake Taupō are closed to swimmers after two wastewater spillages this week.
The Taupō District Council said a pipe failure caused a large overflow this morning near the Kowhai Road pumping station at Rainbow Point, near Taupō.
Signs warning people not to swim were placed along about 700 metres of lakefront.
Contractors used sucker trucks to clean up about 10 cubic metres of material this morning.
It was the second time in three days wastewater leaked into Lake Taupō. A blocked pipe caused a smaller spillage at Two Mile Bay on Monday.
Taupō District Council operational services manager Kevin Strongman said warning signs were in place, telling people not to swim in the affected areas.
"The one that happened this morning is about 400 metres that's been affected, and we've got signs out every 50-odd metres. The first one that happened on Monday, there are signs out for about 200 metres."
He said the swimming restrictions would not be lifted until the water sampling results indicated it was safe.
"We test daily and it takes about 24 hours for those tests to come back."
Mr Strongman said the council expected the water to be clear in three to four days. The council frequently checked and replaced wastewater pipes where necessary.