Video: Paeroa Towing Services.

Reports are coming in from members of the public saying the Ohinemuri River in Karangahake Gorge has turned orange.

Hauraki District Council says they are aware of the issue turning the water in the Ohinemuri River orange.

"This is likely from water coming out of old mine workings," they say on their Facebook page.

"Waikato Regional Council is investigating the issue and advise for safety reasons, please do not enter the water.

"Our Paeroa water supply intake is upstream of this so is not affected however we'll be monitoring the situation carefully."

"Waikato Regional Council is urging people to treat bright orange discolouration of the Ohinemuri River as contaminated," says a Waikato Regional Council spokesperson.

Senior Incident Response Officer Robert Isaac says worst case scenario is the discoloured water is due to a mine shaft collapse, and old mines contain many heavy metals and contaminants.

The Ohinemuri River has turned orange. Photo by Hauraki District Council.

The incident was reported to the council at about 3pm.

Council staff are at the river and are assessing the discoloration.

Isaac says staff have yet to identify the source of the discolouration, which appears to enter the Ohinemuri River downstream of the Waitawheta river.

“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.

"If this is an old mine shaft that has blown out than people should not be using or touching the water.”

The Ohinemuri River has turned orange. Photo by Waikato Regional Council.

"Other scenarios could include a collapsed out forestry dam or other erosion.

Waikato Regional Council ask people to follow their Facebook page for further updates.