A 17-year-old boy was found injured in Sutton High Street just before 7.10pm yesterday (December 5).
Officers, London Ambulance Service crews and an air ambulance were called to the scene.
An incident response officer, an ambulance crew, and a medic in a fast-response car also attended.
The teenager was treated at the scene but was pronounced dead shortly after.
Police enquiries are now ongoing to trace his next of kin.
In an appeal released by Sutton MPS (@MPSSutton) on X, formerly Twitter, today (December 6), officers said no arrests have been made.
Sutton High Street can be seen partially cordoned off by police officers in pictures as the incident is dealt with.
A large yellow tent erected can also be seen in the distance with police tape surrounding it.
Sutton Train Station remains closed with disruption expected until the end of the day.
No arrests have been made following the incident.
A spokesperson for Metropolitan Police said: “Police and LAS were called to Sutton High Street at about 19:08hrs on Tuesday 5 December, following reports that a teenager had been stabbed.
“On arrival officers found a 17-year-old male suffering with stab wounds. He was treated at the scene but sadly died as a result of his injuries.
“Enquiries are ongoing to trace his next of kin.
“No arrests have been made.
“A number of road closures have been put in place at the location, including a full closure of Sutton Train Station.
“An urgent investigation is under way and enquiries are ongoing.”
A spokesperson for London Ambulance Service said: “We were called yesterday (5 December) at 7:02pm to reports of a stabbing on Sutton High Street, SM1.
“We sent a number of resources to the scene, including an incident response officer, an ambulance crew, and a medic in a fast-response car.
“We also dispatched London’s Air Ambulance, which consisted of a trauma team by car.
“Our crews treated a person. Sadly, despite the team’s best efforts, the patient was pronounced dead at the scene.”