A seventh teenager has been arrested in connection with the murder of 14-year-old Paul Erhahon.
The 17-year-old is in custody, along with two 15 year-olds, who are also being questioned at east London police stations, Scotland Yard confirmed.
Paul died from a stab wound to the heart after he was attacked in the foyer of a block of flats in Leytonstone, east London, on Friday.
He was the seventh Londoner aged under 16 to be murdered since the end of January.
Two boys, aged 13 and 14, both appeared at Waltham Forest Youth Court this week accused of Paul's murder.
They are also accused of the attempted murder and grievous bodily harm of a 15-year-old boy and have been remanded in custody to appear at the Old Bailey on April 24.
A 19-year-old man and a 14-year-old boy have been bailed to return in June pending further inquiries.
Paul attended Kingsford Community School in Beckton, east London - the same school as 15-year-old Adam Regis, who was stabbed to death last month.
