A third person, who was injured in the crash, managed to climb a steep, 20m-high bank through long grass from where the car came to rest in a gully, to be found by a passing motorist who called police about 8am yesterday.
That person, not identified as male or female, was taken to Timaru Hospital by ambulance.
It is believed the two who died in the crash were a 21-year-old man and and 18-year-old woman.
The three people were travelling south in a 1992 Nissan Primera over an undulating and twisty section of SH82 south of Waihao Downs before coming down to the Waitaki Plains.
The car failed to negotiate a left-hand bend, crossing into the opposite lane, then off the road and down a steep bank.
The car continued forward until striking a tree and then a fencepost, bouncing into the bottom of the gully beside a creek about 20m below the road surface.
It is believed the crash occurred late on Saturday night, but Acting Sergeant Bryan Ennis, of Timaru, did not know exactly when and the time the injured person managed to climb up the bank.
A crane was called from Timaru to lift the car from the gully on to the road, where it was inspected by the Serious Crash Unit, then on to the truck deck.
Police said it appeared both deceased were not wearing safety belts and speed and alcohol were contributing factors.
Late yesterday, neither of the two persons had been formally identified.
Two units from the Waimate Fire Brigade, police from Waimate and Timaru and a St John ambulance were called.
The road was reduced to a single lane for about five hours.
Elsewhere in New Zealand, a motorist died and several others were injured after a crash near Rotorua on Saturday morning.
The accident happened after a truck and a car collided near the Hell's Gate tourist attraction on State Highway 30 at 11.15am.
In another fatal incident in Rotorua, a pedestrian was killed after being hit by a car about 4.30am yesterday, on SH30, just south of the Rotorua airport. A bus rolled on SH57 near Shannon just before 6pm yesterday, trapping about 40 passengers inside.
About eight people with moderate injuries were taken to Palmerston North Hospital, St John communications manager Mark Tregoweth said.
Police said no other vehicles were involved, and the cause of the crash was unknown.
Additional reporting from The New Zealand Herald/APNZ
