Two more people have been arrested after a 15-year-old boy was stabbed to death in east London.
The teenager was found injured in Woodman Street, Royal Docks, Newham, shortly before 7pm on Friday.
Despite efforts to save him, the boy died at the scene.
The Metropolitan Police said they arrested two people on Sunday morning in connection with the incident - a 17-year-old boy on suspicion of murder and a 28-year-old man on suspicion of attempted murder.
A 25-year-old man arrested on Saturday on suspicion of murder was released with no further action against him, the Met said.
The boy's next of kin have been informed of his death and inquiries into the circumstances were under way over the weekend.
Lawrence Adu said he was a friend of the boy's uncle and had known him "all his life".
Paying tribute to the 15-year-old, Mr Adu, who was also the boy's neighbour, said: "He's a nice young man, very handsome and always laughing."
Detective Chief Inspector Mark Wrigley, from the Met's Specialist Crime Command, said: "These arrests are a positive step in our investigation but we are still working to establish exactly what took place on Friday night.
"There were lots of people in the area at the time and I would appeal for anyone who hasn't yet come forward, to do so.
"The senseless killing of a 15-year-old has understandably shocked the community and I would urge them to help us bring those responsible to justice."
Shortly before, in a separate incident, a 17-year-old boy was taken to hospital after being found with a stab wound and injuries consistent with a corrosive substance in Hounslow, west London.
Anyone with information is urged to call the Met's Specialist Crime Command incident room on 0208 345 3715 or the independent charity Crimestoppers, anonymously, on 0800 555 111
