A 32-year-old man is now the only suspect after multiple people were stabbed on a train, police have confirmed.
A railway staff member remains in a life-threatening condition following the attack on a train from Doncaster to London King's Cross, which stopped in Huntingdon, Cambridgeshire, shortly before 20:00 GMT on Saturday.
A 35-year-old man, who was arrested at the scene, has been released with no further action after it was reported "in good faith" that he had been involved in the attack. Officers later confirmed this was not the case.
On Sunday evening, British Transport Police (BTP) confirmed five casualties had been discharged from hospital.
The force said the suspect, who is from Peterborough, boarded the London North Eastern Railway (LNER) train at the city's station.
