Police are currently attending a crash involving a truck and trailer unit on State Highway 90 about 5km south of Waikoikoi, near Gore.
The truck has overturned with two people inside, police said.
Their conditions are not known. No other vehicles were involved.
Emergency services are at the scene, including a rescue helicopter from Dunedin.
Detours will be in place until the crash is cleared and delays are likely.
A serious crash investigator is at the scene.