A man is being hunted over a sex attack on a teenage girl at the transport interchange in Barnsley.
Detectives have released a CCTV image of a man the believe could hold vital information.
A 13-year-old girl was sexually assaulted by a man at 8pm on Saturday, May 7.
A South Yorkshire Police spokesman said: "police investigating a reported sexual assault in Barnsley have released a CCTV image of a man with distinctive hair, as officers believe he could hold vital information to assist with the investigation and are asking for anyone who thinks his appearance looks familiar to please come forward.
"At around 8pm on Saturday, May 7, a 13-year-old girl was at the Barnsley transport interchange in Midland Street when she was approached by a man unknown to her.
"The man is alleged to have sexually assaulted the girl and when she got onto the bus, he is understood to have also got on the bus with her where he continued to make inappropriate comments.
"When the girl got off the bus, she alerted her family who called police at around 8.55pm that evening.
"Police believe the man pictured could hold useful information and are appealing for him, or for anyone who believes they may know his identity, to please get in touch.
"They are also keen to hear from anyone who may have witnessed the incident at the interchange or on the bus."
Call South Yorkshire Police on 101.