4.31pm: The road has been reopened.
Update: One person has life-threatening head injuries and another has serious injuries following a car and truck collision shortly before 2.14pm today.
The other two occupants of the car have moderate injuries and the condition of the truck driver is not known.
The road was closed, but a single lane has been reopened to allow alternate east and westbound traffic through and motorists are being warned to expect significant delays.
"My advice to motorists heading from Waikato to Tauranga or the western Bay of Plenty is to take an alternative route. From Waikato, take SH5 to Rotorua, then State Highway 36 to Tauranga. Alternatively, you can take State Highway 2 through Waihi to Tauranga," Senior Sergeant Ian Campion said.
"Drivers travelling from Tauranga to Waikato can take the opposite routes."