The car crashed into this roundabout in Swansea

Her friend Amy Williams, 13, from Loughor, remains in a critical condition after being transferred to Cardiff's University of Wales Hospital.

Both girls were thrown from the car, which had been stolen from the Loughor area in the early hours of Friday, when it hit a mini roundabout between Penllergaer and Gorseinon.

Police reported that three youths ran away from the scene of the accident, leaving the teenagers unconscious on the roadside.

They had already arrested a 22-year-old man in connection with the incident. He was released on bail after questioning.

Police made a new arrest Tuesday morning, taking in a 19-year-old from the Gendros area to be quizzed.

Crash scene

"The man was arrested in the early hours of this morning and remains in police custody at Swansea Central police station where he is being questioned," a police spokesman said.

"Inquiries are continuing to trace other people who were thought to be in the vehicle at the time."

On Monday, Sharlene Banfield's elder sister Lisa, 18, appealed to the youths who had fled the crash scene to contact police.

"If the boys who left my sister to die at the roadside have a conscience, please come forward," said Ms Banfield.

"I plead with anyone who has any information in relation to the accident or who knows who was with Sharlene and Amy that night to contact the police.

"Everyone who knew Sharlene loved her. She was a beautiful young girl who you just had to love."

Anyone with information is asked to contact South Wales Police is 01792 456999.