Ohinemuri River near Paeroa has turned bright orange prompting authorities to warn the public, “please do not enter the water.”
For safety reasons, people should not use or even touch the water, authorities caution.
Waikato Regional Council says the public should regard the river as “contaminated” and stay away.
A senior response team official has warned the public to treat the situation as a “worst case scenario” - “as we are getting reports of people standing in the water”.
The incident was reported to council about 3pm on Friday.
The council’s Senior Incident Response Officer Robert Isaac says the discoloured water may be due to a mine shaft collapse. “The old mines contain many heavy metals and contaminants.”
Other scenarios include a collapsed forestry dam or other erosion.
“Until we can ID the source we need to treat this as worst case scenario as we are getting reports of people standing in the water,” says Isaac.
“If this is an old mine shaft that has blown out then people should not be using or touching the water.”
The council says the discolouration appears to enter the Ohinemuri River downstream of Waitawheta River.
Waitawheta River reaches Ohinemuri River at Karangahake, about 5 kilometres east of east of Paeroa.
Hauraki District Council says Paeroa’s water supply is safe to use - but continues to monitor the situation.
“Our Paeroa water supply intake is upstream of this so is not affected however we’ll be monitoring the situation carefully.”