Detectives investigating the murder of a man in Borough on Friday have appealed for witnesses and information.
Detectives from the Metropolitan Police's homicide and major crime command have opened an incident room at Lewisham Police Station.
A post-mortem examination at Greenwich Mortuary on Saturday gave the cause of death as stab wounds.
The dead man has not yet been named by police.
Officers say that they are keeping an open mind regarding any motive for the attack.
The police have released a description of a man they would like to trace in connection with the incident. He is described as a dark skinned black man, short, with short dreadlocked hair, wearing a white short sleeved top, dark coloured trousers and dark coloured footwear.
With him was a taller man for whom no further description has been given.
Any witnesses or anyone with any information is asked to call the incident room on 020 8721 4956, or police via 101, or Crimestoppers anonymously on 0800 555 111.
An 18-year-old from Southwark was arrested by detectives on suspicion of perverting the course of justice. He is currently in custody at a south London police station.