Emergency services were called to the collision near the intersection of Mile Flat Rd and State Highway 1 (Herbert-Hampden Road) about 2.15pm today.
Rescue helicopters were sent to the scene, about 44km south of Oamaru.
In a statement tonight, police confirmed that one person had died.
"Despite the best efforts of emergency personnel, one person was sadly pronounced deceased at the scene."
Police said another person had suffered critical injuries and were being treated at hospital. Two others had minor injuries.
Hato Hone St John said ambulance staff treated two patients and transported them to Dunedin Hospital via helicopters - one in a serious condition, the other in a minor condition.
A white ute on the other side of the road also appeared to have suffered some damage, including to its roof.
Traffic was significantly backed up north of Hampden, he said.
There was a large emergency services presence including two helicopters, two ambulances, three fire trucks and four police cars.
The highway between Hampden and Oamaru was closed about 3.10pm, the NZ Transport Agency/Waka Kotahi said.
A spokesman said road users were urged to avoid SH1/Herbert-Hampden Rd, or delay their journey.
People in the area should follow the directions of emergency services at the crash site.
The Serious Crash Unit attended and police said they were investigating the circumstances of the crash.
- Allied Media
