A teenager has been arrested on suspicion of being involved with a brawl that broke out at an illegal rave in Croydon.
The 18-year-old handed himself into police and has been put into custody at a south London station.
Investigating officers still want to speak to six other men they would like to speak to in connection with disorder following a rave where a teenager died.
Rio Andrew was take to hospital in the early hours of Sunday after falling ill at the party, which was attended by more than 2,000 at a disused sorting office in Cherry Orchard Road.
The 15-year-old aspiring athlete had attended the event with a group of friends before becoming ill after allegedly drinking beer laced with ketamine. He died the following day.
A 19-year-old remains in hospital after falling ill at the rave.
Officers are specifically appealing for the six men featured in CCTV images to come forward - they believe they may hold the key information about disorder that happened during and after the rave.
Police do not believe an of the men are connected to the death of Rio.
Violence broke out when officers put a cordon around the former post office to stop anyone else getting inside. Revellers launched ,missiles, at officers including furniture and fire extinguishers.
Commander Simon Letchford said: "The behaviour of some of those attending this illegal rave and the direct attacks on officers who were there to maintain public safety is completely unacceptable.
"We will identify all those responsible and bring them to justice."
A total of 15 people have now been arrested in connection with the party, nine of who were arrested during the event.