Officers were called at 9.56pm on Saturday (September 6) and a crime scene was put in place at Manor Park on Sunday but has since been closed.
The Metropolitan Police said one victim is being supported by specialist officers.
No arrests have been made at this stage, and a suspect remains outstanding.
Detectives are carrying out enquiries to establish the full circumstances of what happened.
Anyone with information is urged to contact police on 101 or report online.
