A baby in Adelaide has died in a low-speed car crash that police have linked to leaking exhaust fumes.

The 8-month-old boy, a 7-year-old girl and a 33-year-old woman were all found unconscious in their station wagon after it slowed and clipped a tree, then a parked car, in suburban Hilton.

Superintendent Bob Fauser said it appeared they were overcome by carbon monoxide poisoning.

"The indications are that they were ... unconscious before the impact occurred" on Friday night.


Investigators found significant wear to the exhaust and sealing on the car, causing fumes to drift into the cabin.

The family had just dropped someone off at the airport, Fauser said.

"It's a terribly tragic set of circumstances. I cannot begin to understand the trauma that the family must be going through."