An 18-year-old man has been arrested on suspicion of murder after a 17-year-old boy was stabbed following a birthday party in north-west London.
Police and London Ambulance Service were called to Granville Road, Kilburn, at 23:22 BST on Friday following reports of a fight and a stabbing.
A 17-year-old boy was pronounced dead at the scene.
Another teenage boy and a woman in her early 20s were treated at the scene before being taken to hospital.
Formal identification of the boy who died has yet to take place.
Det Ch Insp Mark Rogers said: “We believe that there was a fight following a birthday party, which would have been attended by a number of people.
“I would urge anyone who was there, and who has not yet spoken with officers, to please come forward.
“It is vital that we establish what happened.”
Ch Supt Dan Knowles, in charge of the North West Command Unit which polices Kilburn, said: “I know that the community will be shocked by this incident in which a young man has lost his life.”