Four men have been arrested on suspicion of murder, following the fatal stabbing of 16-year-old John Ogunjobi last week, Metropolitan Police have said.
The men - aged 22, 20, 21 and 23 - have been taken into custody at south London police stations for questioning.
Officers have returned to the scene of the crime in Tulse Hill to appeal for witnesses.
“I am appealing to anyone who has information that could assist this investigation to come forward and speak to police,” DCI Vandenbergh said.
“We believe the victim was attacked by a number of suspects and the altercation would have undoubtedly drawn the attention of those who were in the vicinity.
“Did you see or hear anything? If so, no matter how insignificant you think it may be, please call - your information could prove to be crucial.”
Police are also asking for anyone who may have captured footage or photographs of the incident on their phones to come forward.
Authorities were called to Greenleaf Close, Tulse Hill, at just before 11PM on Monday 5 November.
Despite the efforts of paramedics, Ogunjobi was pronounced dead at the scene shortly after 11.30PM.
A post-mortem examination saw his cause of death recorded as a stab wound.
His death marked the 119th homocide in London this year and was the fifth fatal stabbing in the space of six days in south London.