A truck and trailer unit has rolled on State Highway 6, near Nelson, blocking the highway.
A police spokeswoman said police arrived at the scene, on Whangamoa Rd, between Kokorua Rd and Hori Bay Rd, just after 1pm.
The road was blocked in both directions and police were diverting traffic.
A traffic alert on the NZTA website at 1pm said a crash had been reported to emergency services and delays were possible. An update would be provided when more information was available.
More to come