Police in England on Sunday ruled out speculation that a mass stabbing on a passenger train that injured 11 people was a terrorist attack.

"At this stage, there is nothing to suggest that this is a terrorist incident," British Transport Police Superintendent John Loveless told UK media.

He continued: "At this early stage, it would not be appropriate to speculate on the causes of the incident."

What do we know?

On Saturday evening, a mass stabbing on a London-bound train near Huntingdon, Cambridgeshire, left 11 passengers hospitalized, nine with life-threatening injuries.

One person remains in a life-threatening condition, and five of the injured passengers have been discharged from the hospital, police said Sunday.

"Armed police from Cambridgeshire Police boarded the train and arrested two people in connection to the incident who have been taken to police custody," police said in a statement.

Loveless confirmed that the pair were being held on suspicion of attempted murder.

Later on Sunday, one of the suspects was released without charge and only a 32-year-old Black British man remained in custody and is the only suspect. 

"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," British Transport Police Deputy Chief Constable Stuart Cundy said. "Having viewed the CCTV from the train, the actions of the member of rail staff were nothing short of heroic and undoubtedly saved people's lives."

The train involved was the 6:25 p.m. from Doncaster to King's Cross in London, British Transport Police said.

PM Keir Starmer, King Charles decry knife attack

In a post on X Saturday night, UK Prime Minister Keir Starmer said the incident was "deeply concerning" and that his thoughts were with those affected. He also thanked emergency services for their response.

British Home Secretary Shabana Mahmood said she was "deeply saddened to hear about the stabbings" and that her "thoughts go out to all those affected."

She urged people to avoid commenting or speculating "at this early stage" of the investigation.

Britain's King Charles III and Queen Camilla said on Sunday they were "truly appalled and shocked to hear of the dreadful knife attack."

"Our deepest sympathy and thoughts are with those affected, and their loved ones," Charles said.

Edited by: Karl Sexton and Darko Janjevic