The incident occurred shortly after 6pm on November 17 at Balham tube station.
According to the British Transport Police, a fight broke out on the southbound platform between two groups of people.
During the incident, one of the group members is alleged to have pulled out a knife before they were chased out of the station.
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BTP has since released CCTV images of a group of people it believes may have information that could help with the investigation.
If you recognise any of the people pictured, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 511 of 17 November.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.
