South Wales Police is investigating a serious road traffic collision which happened earlier on Saturday (Oct 3) in Penlan, Swansea.
A green Mercedes A Class motor vehicle overturned on Clwyd Road near its junction with Penderry Road, at 4.07am.
A 21-year-old man sustained serious injuries and was taken to the University Hospital of Wales, Cardiff where his condition is described as critical..
Officers are keen to identify a second man who is also believed to have been in the car but left the scene prior to their attendance.
Members of the public are thanked for their patience, while investigation work is carried out at the scene and for their patience during the road closures.
Witnesses to the incident, or the manner in which the green Mercedes-Benz was being driven prior to the collision, are asked to please contact South Wales Police on 101 and quote occurrence number *360836.