A woman is in a critical condition in hospital after two cars collided, causing a police car to roll "several times" and the other vehicle to end up in a front yard in Adelaide's south.
Police were travelling on Seaview Road in Victor Harbor just after 1.30am when their car collided with a Ford sedan, trapping two people inside the wreckage.
The force of the collision tore the back cabin off the police car.
South Australian Police Minister Joe Szakacs said he was told it was a "terrible set of circumstances".
"It was a collision that wasn't part of a police pursuit or any other operational matter," Szakacs said.
Both senior constables in the car received minor injuries, were treated at South Coast Hospital and have since been discharged.
The 48-year-old driver of the Ford sustained serious, life-threatening injuries and was taken to the Flinders Medical Centre.
The male passenger in the Ford was not injured.
Seaview Road was closed for several hours but has now reopened.
Investigations by the major crash department are ongoing.