Emergency helicopters from three cities have been sent to the scene of a major crash on State Highway One in Clarence, north of Kaikо̄ura.
SH1 has been closed and diversions are in place.
Two people were being treated, one with serious injuries, St John said.
Emergency helicopters from Christchurch, Wellington and Nelson were sent to the scene, St John said.
Police say they were called about 9.30am to the crash near the intersection with Clarence Valley Rd.
People are being told to avoid the area.
Southbound traffic from Blenheim should use SH63, SH6, SH65, SH7 and back onto SH1 at Waipara.
The reverse route should be used for northbound traffic.
More to come.