The 15-year-old boy arrested in connection with the murder of Wesley Sterling has been bailed.
Sixteen-year-old Wesley was stabbed to death at a 16th birthday party at Croydon Arena just after midnight on Sunday morning.
The former St Mary's pupil was a guest at the party.
The 15-year-old boy was arrested on suspicion of murder and possession of an offensive weapon. He has been bailed until June.
A spokesman said: "Police are appealing for information about the stabbing and an earlier incident at the same venue.
"At approximately 11pm Saturday April 17 a group of six to eight males tried to gate crash the same venue which was holding a 16th birthday celebration.
Police and ambulance crews were called after a disturbance the scene on Albert Road, South Norwood at 12.18am, where they found the 16-year-old, who had been stabbed in the chest, in a walkway near the club.
Detective Inspector Alison Hepworth investigating from HSCC said: "We know there were many guests at the party and would appeal to them to come forward with information on what happened."
More than a thousand friends have joined tribute pages set up on facebook to the young man.
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