Police are trying to trace witnesses who saw a woman being sexually assaulted on a train travelling from Sheffield to Hull.
The victim was assaulted between 21:00 and 21:45 BST on 21 September by a man who sat next to her and began to make inappropriate comments, British Transport Police (BTP) said.
A passenger reported the incident to the conductor and police officers met the train at Hull Paragon Interchange where they arrested a man in his 40s on suspicion of sexual assault. He has since been bailed.
A BTP spokesperson said: “Officers believe several members of the public saw the incident and the discomfort of the woman and would urge anyone who witnessed anything to get in touch.”