The crash happened on Monday night on the A483 at Cadle.
Two people are in hospital - one in a critical condition - after a three car crash in Swansea last night
The collision happened on the A483 at Cadle involving a red Mini Cooper, a white BMW and a blue Ford Mondeo which was travelling in the opposite direction to the Mini and the BMW.
A 20 year old man has been arrested on suspicion of dangerous driving and is being questioned by police.
The road was closed in both direction for several hours and motorists are thanked for their patience and cooperation.
Officers are now appealing to anyone who witnessed the collision or the manner in which any of the vehicles were being driven prior to it, to come forward.
Anyone with dash-cam footage which may assist the investigation is also asked to make contact.
Please call 101, quoting occurrence 2000068523.