A 15-year-old girl was raped in Abingdon's multi-storey car park.
The incident happened on level seven of the Charter Way car park between 4pm and 4.45pm on Tuesday, July 3.
The crime was reported on Friday, July 6, but police only released the details last night when they said they needed a potential witness to come forward.
A 17-year-old youth from Witney has been arrested in connection with the incident and bailed until September 9.
Det Sgt Darren Cartwright, from Abingdon CID, said: “Although we have made an arrest, we still need to trace witnesses.
“The victim believes that she saw a woman on level seven just after the incident and I would be keen to trace her and any other witnesses.”