Two teenagers arrested in connection with the stabbing of a rail ticket inspector remain in custody.
The 42-year-old inspector was attacked after challenging two youths travelling without tickets at East Tilbury station in Essex just before 9pm on Friday.
British Transport Police said two people were arrested on Sunday in connection with the stabbing on the 8.20pm c2c service from Southend Central to Fenchurch Street in London.
The suspects, a 19-year-old man and a 17-year-old boy, were arrested in Tilbury on suspicion of causing grievous bodily harm and taken to a police station in Southend for questioning.
The inspector was taken to Basildon University Hospital where he received three stitches for his wound before being discharged on Saturday night.