An 18-year-old man has been stabbed to death in west London.
Police were called to High Street in Uxbridge at about 16:40 GMT on Thursday.
The victim, who had been stabbed in the chest, was taken to hospital but pronounced dead less than an hour later.
Another teenage boy was also stabbed in the attack. A 17-year-old boy has been arrested on suspicion of murder, Scotland Yard said.
The other injured teenager suffered a knife injury to his ear, but his injuries were not considered life-threatening.
The Met has granted itself enhanced stop-and-search powers, under section 60 of the Criminal Justice and Public Order Act.
This allows officers to search anyone in a designated area without “reasonable grounds”.
Det Ch Insp Noel McHugh described the stabbing as “a tragic loss of life”.