A witness of a mass stabbing on a London-bound train has described how she fled through carriages to escape the attack, saying she didn't know if she'd be the next to be stabbed.

Student Amira Ostalski told British broadcaster Sky News she was travelling to London for a Saturday night out with her friend when the incident took place.

"Everyone's running, a guy next to me is holding his arm covered in blood saying he got stabbed and he was right next to me on the train, so that was quite terrifying," she told Sky.

In a statement Sunday evening, police said the suspect is a 32-year-old British man who remains in custody on suspicion of attempted murder.

A second man initially arrested as a suspect was released without charge after it was determined the 35-year-old was not involved.

Police said they are not treating the stabbings as an act of terror and are confident they are not looking for anyone else in connection with the attack.

They have not disclosed a possible motive or the type of knife used.

Six people remained in hospitals Sunday, one of them in a life-threatening condition.

Police said he is a staff member of the train's operator, London North Eastern Railway, or LNER, which operates the East Coast Mainline services in the U.K.

The five others injured during the attack on Saturday evening have been discharged from hospitals.