Investigations are taking place after a woman was reportedly subject to homophobic comments at Pengam railway station.
A woman reported that she was the subject of homophobic comments on the platform at the station.
The incident happened at around 2.15pm on Sunday, December 29.
The suspect got on the train at Pengam and got off at Cardiff Central station.
Anyone with relevant information can contact British Transport Police by texting 61016 or by calling 0800 405 040, quoting reference 287 of 30/12/19.
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.
This article was amended to remove a picture of a person British Transport Police wanted to speak with in connection with the incident.