The collision between a car and a truck happened at the intersection of Moeraki Boulders Rd and Hampden-Palmerston Road, near Hampden, about 5.10pm today.
About 5.30pm, a Fire and Emergency New Zealand (Fenz) spokesman said crews were working to remove a person from a vehicle and police said initial reports indicated there had been injuries.
A Hato Hone St John spokesman later confirmed that a helicopter transported a critically injured patient to hospital.
Two other patients were treated at the scene.
Ambulances from Oamaru and Palmerston responded.
The Fenz spokesman said crews from Hampden, Palmerston and Weston were called to the crash.
It was suitable for light vehicles only, she said.
An Otago Daily Times reporter said about 6pm that southbound traffic was backed up about 2km from the scene.
Waka Kotahi/ NZ Transport Agency advised at 6.40pm that SH1 had reopened under stop/go measures and to expect delays as congestion eased.
