Four people were injured in a two-vehicle crash on the Rakaia Highway near Newland overnight.

A St John spokesman said they were notified of the crash just after 10pm and responded with two ambulances, a first response unit, and a helicopter.

One patient was airlifted to Christchurch Hospital in serious condition, while another was taken to Ashburton Hospital with moderate injuries.

Two other patients were assessed at the scene.

A police spokesman said the road was blocked until around 1am.