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."
2.51pm: The person trapped in a car after a crash with a truck has been rescued.
A fire communications spokesperson said the patient had been extracted from the vehicle and was being treated by ambulance.
Ambulance were also treating two other patients, at the scene of the crash on the intersection of Poripori Rd and SH29.
He said fire services were assisting police with road closure.
A reporter at the scene said police were turning cars away at the Omanuwa Falls Power Station turnoff.
Earlier: At least one person is trapped in a car following a crash in the Kaimai Range this afternoon.
The crash happened about 2.10pm on State Highway 29 between a light truck and the car.
Firefighters are working to free the person.
Motorists are advised to avoid travelling over the range until the scene can be cleared.
A reporter heading to the scene said traffic is heavily congested heading west over the Kaimai Range, almost at a standstill.