Water supplies to nearly 600 Taupō residents have been reinstated now that algae has tested non-toxic.
Sign warning of algal bloom at Lake Taupō Photo: RNZ / Rebekah Parsons-King
Intakes at Hatepe and Motuoapa were shut down on Friday after a drone inspection revealed a weed-like substance near the pipe inlet.
Scientists collected samples from algal blooms on Saturday.
A Taupō emergency management worker at the Hatepe village water supply on Friday. Photo: RNZ / Rebekah Parsons-King
One-hundred residents at Hatepe and 460 at Motuoapa were switched to tank water while tests were conducted.
Popular swimming spots around the lake including Kinloch and Acacia Bays and the main town lake front remain closed to swimmers. The swim leg of an Ironman event being held on Saturday was cancelled.
Taupo District Council's chief executive Gareth Green said these sites are still being monitored and it could be weeks before they are re-opened.
"We still have six locations around the lake where the health warning applies for contact recreation."
"There's testing happening right now on the toxicity levels of the algae, so in those locations those first results will be coming back today, however it's unlikely that the health warning will be able to be lifted for some time. What the medical officer of health needs to see is continual reduction of the levels of algae before that can happen."
Some of the algae in Lake Taupō Photo: Waikato Regional Council
The sites are sign-posted, warning people from entering the water.
Mr Green said spots that did not have warning signs were safe to swim in, but asked people to remain cautious.
"There are a large number of beaches around the lake which have been tested and come out clear, which is brilliant, and all we're asking is that people right round the lake watch out for algae and if they see it then to avoid it and don't come into contact with it."
He said there was no timeframe on when the contaminated sites would be swimmable again.
"It is a wait and see, and the medical officer of health makes the decision based on those levels coming down and a consistent decrease over time as well as predictions around things like weather."
Mr Green said the Waikato River, which feeds Lake Taupo, had tested negative for toxic algae.
A medical officer of health said people should avoid eating shellfish and koura sourced from all parts of the lake.
Dr Neil de Wet said this type of seafood may be toxic but trout and other fish were unlikely to be harmful as long as they were properly gutted and washed.
"The toxin might accumulate in the gut and the liver, but obviously no one eats that so the important thing is to gut the fish and wash it well in fresh, clean water, and it would be safe to eat."
Toxic algae found in Southland river
Potentially toxic algae has been found in the Aparima River in Southland.
The Southland regional council found the cyanobacteria in the river at Thornbury in Western Southland.
The council said the algae occurred naturally but could increase rapidly during warmer weather or because of high levels of nutrient run-off from farming.
It said the forecast long dry summer coming may lead to more algal blooms so it would be monitoring lakes and rivers closely.