A 16-year-old boy found fatally stabbed in a stairwell of a block of flats after a party was been named by police.
Peter Hagan was pronounced dead after being discovered on the ground floor of the block in Wandsworth, south west London, at 1.30am yesterday.
A Metropolitan Police spokesman said: "Although we await formal identification, we are satisfied the victim was Peter Hagan."
A post-mortem examination started yesterday and was due to resume later today.
A murder investigation has been launched and an incident room has opened at Sutton, south London, under Detective Chief Inspector Nick Scola, of the Homicide and Serious Crime Command.
Nine people have been arrested in connection with the inquiry, Scotland Yard said. Eight have been bailed pending further inquiries and the ninth currently remains in custody.
Police cordoned off a stretch of road outside Albon House in Neville Gill Close, Wandsworth, yesterday as forensics teams examined the scene.
Witnesses or anyone with information are asked to contact the incident room on 020 8721 4005 or call Crimestoppers, anonymously, on 0800 555 111.