Detectives investigating the murder of Chris Foster in Borough High Street on Friday night believe that he was not the intended victim of his attackers.
Mr Foster died in hospital in the early hours of Saturday morning having been stabbed whilst having a cigarette outside St Christopher's Inn in Borough High Street before midnight on Friday night.
DCI John Sandlin, who is leading the investigation, said: "At this stage of our investigation, this appears to be a case of mistaken identity.
"I am keen to identify a group of males who were seen running from St Christopher's Inn along Borough High Street towards Elephant and Castle immediately after the stabbing."
Anyone with information that may assist the investigation should call the incident room on 020 8345 3865. To remain anonymous call Crimestoppers on 0800 555 111.
A 32-year-old woman was arrested on Sunday on suspicion of assisting an offender. She was taken to an east London police station where she remains in custody.
Several of the courtyards on the eastern side of Borough High Street remained sealed off on Sunday morning.
Floral tributes to Mr Foster, a 34-year-old father of one, have been laid outside St Christopher's Inn.