“We’re conducting urgent enquiries to establish what has happened, and it could take some time before we are in a position to confirm anything further,” British Transport Police Chief Superintendent Chris Casey said. “At this early stage it would not be appropriate to speculate on the causes of the incident.”

Cambridgeshire police said they were called at 1939 GMT after reports that multiple people had been stabbed on the 1825 service from Doncaster in northern England to London King’s Cross.

The train stopped at Huntingdon, with armed officers seen entering the train in videos on social media.

“Armed officers attended and the train was stopped at Huntingdon, where two men were arrested,” the police said.