One suspect, 35, released with 'no further action' after Huntingdon train mass stabbing

"A 35-year-old man from London who was also arrested at the scene has been released with no further action," BTP said.

"It was reported in good faith to officers responding to the incident that he was involved in the attack, and following enquiries we can confirm that he was not involved."

Deputy Chief Constable Stuart Cundy said the "investigation is moving at pace and we are confident we are not looking for anyone else in connection to the incident".

"As would be expected, specialist detectives are looking into the background of the suspect we have in custody and the events that led up to the attack," he added.

It comes as police confirmed "five casualties have now been discharged from hospital".

"One remains in a life threatening condition," police added.

"This casualty is a member of LNER rail staff who was on the train at the time and tried to stop the attacker.

"Detectives have reviewed the CCTV from the train and it is clear his actions were nothing short of heroic and undoubtedly saved many people's lives."

Police previously said there was "nothing to suggest" the stabbing is terror-related.

The force further said the suspect boarded the Doncaster to London King's Cross service at Peterborough.

According to The Telegraph, police say the knife used to stab victims on the train was recovered by police officers at the scene.

Witnesses on the train described seeing the attacker with a large bloodied kitchen knife as he made his way through carriages.

LNER Managing Director David Horne said: "We are deeply shocked and saddened by yesterday's incident and our thoughts and prayers are with everyone affected, particularly our colleague who remains in a life-threatening condition, and their family".

"I would like to thank the emergency services for their quick and professional response and the care they provided to those injured," he added.

"I would also like to recognise the driver, crew and our operational response colleagues for their bravery and quick actions.

“This is a deeply upsetting incident.

"Over the coming days we will continue to co-operate with the authorities involved and will do everything we can to support our customers and colleagues during this very difficult time."

North East of England organiser of Britain's trade union for train drivers, Aslef, said the driver was "shaken up", but he was receiving support.

Nigel Roebuck said: "We have been in touch with the driver overnight and I spoke to him this morning".

"In all honesty it’s not a time to rake over. Our primary concern along with LNER is to make sure that he’s looked after, supported and can face whatever comes in the process in the next few days," he added.

Mr Roebuck told Sky News that the driver is "good".

"He was clearly shaken up, you know. And obviously we didn't kind of get ... too into detail about things," he added.

"We just basically said ... you know where we are if you need us, the lines are open for us.

"And I think LNER have probably done the same with him. So he's getting a great level of support, and that's good."