State Highway 29 on the Waikato side of the Kaimai Range is closed following a crash.
It occurred between State Highway 28 and Poripori Road on Tuesday afternoon.
Emergency services are at the scene and motorists are being warned to be prepared for long delays.
Detours are available.
Waka Kotahi, the NZ Transport Agency said Tauranga traffic for north should use SH2 via Karangahake Gorge.
From Matamata, use SH24, SH28, SH5 or SH36.
Waka Kotahi said motorists should consider delaying their journey.