Emergency services are attending a serious crash in the Timaru district, police say.
The two-vehicle crash happened at the intersection of Rangitata-Orari Bridge Highway and Orari-Rangitata Highway (SH79 and SH1) just before 9.30am.
"Two people in one of the vehicles were trapped for a time, and are in critical condition," police said.
A helicopter was called to transport the pair to hospital.
The road is blocked, and diversions are in place around the scene.
The serious crash unit had been advised, police said.