A woman was allegedly coughed at, verbally abused and hit with a can on a train at Grimsby train station.
British Transport Police said the incident happened at 3.40pm on Tuesday, April 28 after the victim told the suspect not to sit so close as it was an empty carriage.
She suffered slight reddening to her wrist where she was hit with the can.
British Transport Police released a CCTV image on Thursday, May 28 of a woman officers would like to speak to, who may have information that could help with the investigation.
The force did not specify whether the woman is a suspect or a witness.
Anyone with information, or who recognises the woman, is urged to contact BTP by texting 61016, or by calling 0800 40 50 40, quoting reference number 222 of 28/04/20.
Alternatively, it can be reported through the independent charity Crimestoppers anonymously on 0800 555 111.