Three men arrested in connection with the fatal stabbing of Adam Regis have been released without charge.
Adam, 15, from Plaistow, was stabbed to death in Beckton, east London, on Saturday evening.
A police statement said no further action would be taken against the men, aged 22, 20, and 19, who were arrested in Beckton on Tuesday night.
A 17-year-old detained separately on Tuesday in relation to the murder was released on police bail earlier.
Adam, who was the nephew of Olympic sprinter John Regis, suffered a wound to the chest and abdomen when he was attacked at the junction of Boundary Road and Kingsland Road in Plaistow.
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.