The Daily Mail has reported that witnesses in the area saw a group of schoolchildren get off the No 60 bus near the Whitgift Centre and an argument between a girl and boy, both dressed in school uniforms, escalated onto a busy street.

They also said that the dispute is alleged to have begun after a boy attempted to give a girl flowers, with another witness stating that she overheard the girl saying that she wanted to end their relationship.

A large police cordon was in place as the police investigation into the stabbing continued, with forensics officers and a dog handler among those working at the scene.

Pictures show forensics collecting a bouquet of red roses that were left on the ground at the scene.

The flowers have been put into a container, bagged, and removed from the area.

Another image shows a forensic investigator lay different flowers given by members of the public at the scene in tribute to the pupil who died.

A forensic investigator lay flowers given by members of the public at the scene near the Whitgift shopping centre in Croydon (Image: PA)

A 17-year-old boy was arrested in New Addington around 75 minutes after the girl was stabbed to death.

Emergency services were first called to Wellesley Road in Croydon at around 8.30am after reports of the incident.

Both the land and air ambulance attended but she was pronounced dead at the scene 50 minutes later.

It is believed that the teenager arrested knew the victim and he currently remains in police custody.

Security worker Victor Asare told the PA news agency that blood ran “like water” and members of the public rushed to help after the girl was attacked In Croydon, south London, on Wednesday.

Mr Asare said: “The blood was coming like water.

“A lot of people came, everyone came off the bus. (The suspect) ran away. Everybody was crying and screaming. The girl was on the floor.

“We tried to catch him and a lot of people tried to save the girl. I was so shocked, I was shaken. It’s somebody’s daughter.

“I finished work but couldn’t sleep, so came back, I wanted to see if the girl was OK.”

He said that the girl, who was wearing a green school blazer, looked as if she “didn’t want the boy to come closer” before he stabbed her with a knife that was “black, thin and about a foot long”.

A bus driver and a passer-by were seen desperately trying to save the girl before emergency services arrived, with police at the scene in Wellesley Road in Croydon within two minutes.

A mother of two, who wanted to be named only as Bridget, said: “I was on the bus before and came off and walked back down, I saw them resuscitating her.

“The driver was holding her, and a lady.

“The emergency services were already here when I walked back.”

She said two other schoolgirls, believed to be the victim’s friends, were trying to get back through the police cordon but were held back.

James Watkins, from Mainz World which runs prevention and intervention projects for children and young people, was with the girl’s family at the scene between 9am and 10am.

He said: “They were devastated and I would say more importantly in shock, I don’t think it feels real for them.”

The girl who died was a pupil at Old Palace of John Whitgift School, a private girls’ school in Croydon.

The school released a statement that said: “We are deeply shocked by the senseless and tragic death of our much-loved and valued friend and pupil.

“It will take some time for the Old Palace community to come to terms with this terrible news, and we will offer support to our pupils as we try to do so.

“Above all, we send our love and deepest sympathies to the girl’s family at this unimaginably distressing time.”

Witnesses or anyone with information can contact police on 101 quoting reference CAD 1601/27Sep, to remain anonymous contact Crimestoppers on 0800 555111 or online.