Waikato Regional Council is warning that chemicals on board a truck that crashed on the Kaimai Ranges this morning might have entered a nearby stream.
It's understood the truck rolled on State Highway 29, between Rapurapu Kauri Track and Kaimai Mamaku Lookout, shortly after 6am today.
The truck was carrying large containers filled with sodium hydroxide, with approximately 3000 litres spilling from the truck, resulting in the closure of the Kaimai Ranges.
Emergency services are in attendance and a detour is in place.
The council's incident response team is attending the scene to assess the environmental impact of the incident.