The victim of the murder in Harper Road has been named as Lyle Tulloch. He was aged 15.
The teenager was stabbed in a stairwell at Newall House, a block of flats on the Rockingham Estate in Harper Road.
Four male youths were arrested yesterday. One has now been released. The three others have all been bailed to return to a London police station next month.
A post mortem held at Greenwich mortuary gave the cause of death as stab wounds and haemorrhaging.
Police are still appealing for witesses and information. Anyone who can assist should call the incident room on 020 8721 4155.
Or if you wish to remain anonymous please call Crimestoppers on 0800 555 111.