Drivers are being warned to expect lengthy delays on State Highway 29 through the Kaimai Range following a truck breakdown.
NZ Transport Agency Waka Kotahi said the highway is operating under stop/go traffic management just after the SH28 intersection, between Tauranga and Te Poi.
Police were first notified around 7.50am after a truck broke down on the Matamata side of the summit. A second truck then broke down at the same location about 8.15am, further compounding delays.
While one lane remains open, traffic has built up significantly, with motorists facing extensive delays, police said.
Authorities say congestion is likely to continue for several hours, and the highway may remain partially blocked for much of the day.
Road users are being urged to delay travel if possible, avoid the area, or allow significant extra time for their journeys.