A central London Underground station was shut after a teen was injured on a train.
British Transport Police say they were called to Knightsbridge Station at 3.37pm on Wednesday and said a 17-year-old boy was rushed to hospital with "life-changing" injuries.
Passengers tweeted that they saw "blood on the escalators", MyLondon reports.
Another eyewitness tweeted to say they saw "someone stretchered out of Knightsbridge tube station wrapped in foil".
They added: "Police carrying evidence bags full of bloody clothes. Incident, police and ambulance vehicles were all at the scene."
Police confirmed the boy had not been stabbed and that he suffered a "head injury".
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Paramedics were also at the scene before rushing him to a hospital to receive further treatment.
Eyewitnesses say there were "police and ambulances" everywhere.
The London Ambulance Service confirmed members of their Hazardous Area Response Team were deployed at the scene.
Transport for London said the station had been shut for more than two hours while authorities worked to treat the man.
A spokesperson for the force said: “Officers were called to Knightsbridge station at 3.37pm on April 20 following reports of a young person injured on a train. Specialist officers and paramedics attended, and the 17-year-old boy was taken to hospital for treatment to injuries which are believed to be life-changing."
The incident is not being treated as suspicious and it has been referred to the Rail Accident Investigation Branch. Knightsbridge Tube station reopened shortly before 6pm.
A London Ambulance Service spokesperson said: "We were called today at 3.39pm today (20 April) to reports of an incident at Knightsbridge Underground Station.
“We have sent an ambulance crew, an incident response officer, an advanced paramedic practitioner and members of our Hazardous Area Response Team. We also dispatched medics from London’s Air Ambulance.
“Working alongside colleagues from other emergency services, our crews have treated a man for injuries at the scene, and are now taking him as a priority to hospital.”
