Police are on the scene at Watford Junction station where a man has reportedly assaulted station staff.
Police were called just after 12 noon to reports of an assault at the station.
Two units from Hertfordshire Constabulary attended the scene, as well as several from the British Transport Police.
An eyewitness said around six members of staff were restraining a man close to the barriers, and that he sounded “quite upset”.
A man has been arrested on suspicion of common assault.