State Highway 1 in the Canterbury region is blocked after a truck and car collided on Monday.
Emergency services are responding to a serious crash on State Highway 1 (Omihi Road) in Greta Valley.
Two people are in critical condition and another two have minor injuries. A helicopter has been deployed and diversions are in place at Waipara and Greta Valley on State Highway 1.
Motorists are advised to expect delays and to avoid the area.