Police said they received reports of the crash, north of Twizel on State Highway 8 near the intersection with SH80 (the Mount Cook road), just before 10:30am.
Hato Hone St John said several response vehicles and three helicopters were sent to the scene, and medics assessed nine people.
Three people sustained serious injuries - one was airlifted to Christchurch Hospital and two others to Dunedin Hospital. Six people with minor injuries were treated at the scene.
SH8 was closed for several hours, but NZ Transport Agency Waka Kotahi advised shortly after 2pm it had reopened
It's the latest in a spate of serious accidents in the area in recent days.
Several Chinese tourists were injured on Thursday when two buses rolled in icy conditions on SH8 a little way north of today's crash, and there were more delays on Friday when a truck and trailer unit rolled off the highway further south, nearer Twizel. No-one was hurt in that accident.
Parts of inland Canterbury have been beset by freezing foggy conditions for much of the past two weeks, and temperatures have often hovered around 0degC for entire days.
A weather station reading on MetService's website showed Pukaki sitting on 1degC at 12.15pm, and the Mackenzie Country Weather NZ Facebook page said there was dense fog in the area again today.
- ODT Online/additional reporting RNZ
