Police say three teenage boys have been killed after a car was driven at speed into a bus stop.
All three boys, believed to be aged around 16, were declared dead at the scene, and the 28-year-old driver of a black Audi was arrested and taken to hospital for treatment.
A spokesperson for the Metropolitan police has issued an urgent appeal for witnesses, and said the incident is not being treated as terror related.
Police were called to Shepiston Lane in Hayes at 8.41pm on Friday night following reports of a road traffic collision.
Paramedics were also called to the scene but were unable to save the boys, who have yet to be formally identified.
Other teenagers standing with the group at the bus stop, which is close to the Esso petrol station, were unharmed in the crash.
All of the next of kin of the deceased have been informed, the Met Police said.
Investigators have said they are still trying to establish the sequence of events that led up to the collision, and whether there were any other occupants in the vehicle.
The road was closed while the incident was investigated, but the closure has since been lifted.
Officers from the Met's Road and Transport Policing command have urged anyone who may have witnessed the crash to come forward.
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 it up to it? I would urge you to speak to us to assist us with our investigation."
Additional reporting by PA
