A woman was sexually assaulted at Uphall Station and British Transport Police are now appealing for information.
The 45-year-old victim was boarding the 06.54 service to Edinburgh Waverley on Saturday, November 28, when she was touched inappropriately from behind by one of a group of youths who got on the train at the same time.
Officers investigating the incident are reviewing CCTV from the train and the station in an attempt to identify the culprit.
The person responsible is described as being aged between 15-19 years old, slim, with brown hair and wearing a blue t-shirt.
Detective Constable Paul Farquhar is appealing for anyone who may have witnessed the assault to contact British Transport Police.
He said: “This assault left the victim upset and I am hopeful that anyone who was at the station or on the train and has information which can identify those involved will feel able to get in touch.”
Anyone with information can contact British Transport Police on 0800 40 50 40 or by texting 61016. Information can also be given to Crimestoppers on 0800 555 111.