Two young people were injured when a car overturned after hitting boulders they were sitting on at the side of a road, say South Wales Police.
It happened at 1845 BST on Thursday at Garth Road, Ynystawe, Swansea, and involved a green Renault Clio.
Police said the two "young males" on the boulders needed hospital treatment.
Officers are appealing for any witnesses to contact them on 101, 01792 456999 or via Crimestoppers on 0800 555 111.
They said also it appeared that the Clio may have been accompanied by another car, a small, silver Citroen or Peugeot-type vehicle.