Officers and London Ambulance Service colleagues attended.
A group of teenagers were standing near a bus stop when a car, a black Audi, is believed to have collided with three of them.
Three of them died at the scene, but the other teens were uninjured.
A 28-year-old man who was inside the vehicle was arrested and then taken to a west London hospital for treatment.
He will be taken into custody once he is discharged after the incident at 8.41pm last night.
Road closures were put in place while the incident was dealt with but have since been lifted.
Detective Jane Shaw, of the Serious Collision Investigation Unit, said: “These are horrific circumstances that have resulted in three young people losing their lives; I need anyone who saw what happened to contact police immediately.
“Did you see this Audi before the collision, or in the moments leading up to it? I would urge you to speak to us to assist us with our investigation.”
Police clarified the incident is not being treated as terror related.
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