At the early stages, he said it appeared to be a head-on collision.
The two drivers were both the only occupants of their vehicles and both died at the scene.
The area was closed to all traffic, with diversions put in place at Delamaine Street, Hinds and at State Highway 79, Rangitata, with a large number of vehicles asked to turn around.
One witness at the scene said the car had flipped upside down upon colliding with the truck.
Another member of the public believed police had been alerted to the dangerous behaviour of the driver shortly before the incident occurred.
The crash appeared to have occurred in the northbound lane.
In October and November 2017, two crashes occurred near the same intersection, injuring a total of eight people.
Just last Friday a serious crash occurred slightly further south, at the intersection between State Highway 1 and Rangitata Island Road, leaving one person critically injured and three people with minor injuries.
Yesterday afternoon, Dean expected police would be spending "some time" piecing together what had happened. However, he said they were aware of the need to minimise the impact for other drivers slowed down by the diversions.
The crash takes the national road toll to 291 people in the year to date.
- Additional reporting by the Ashburton Guardian.