Police investigating the murder of schoolboy Adam Regis have made three further arrests in the inquiry.
The three men, aged 22, 20 and 19, were detained at an address in Beckton, east London, following the earlier arrest of a 17-year-old youth.
Adam, 15, from Plaistow, was stabbed to death in an east London street on Saturday evening.
The three latest suspects were arrested on Tuesday evening and are being held at separate police stations.
Adam, who was the nephew of Olympic sprinter John Regis, suffered a wound to the chest and abdomen at the junction of Boundary Road and Kingsland Road in Plaistow.
The 17-year-old male suspect was arrested at an address in East Ham in the early hours of Tuesday morning and he was later taken to an east London police station for questioning.
A Scotland Yard spokesman said: "We stress that the investigation continues and that all our points of appeal remain. All lines of inquiry do remain open."
Adam is thought to have been attacked as he made his way home from the Showcase Cinema in Beckton, sometime after 2100 GMT.