Police were called to Coburg Crescent, SW2 shortly before 5.30pm on Friday, 15 January following reports of a gunshot.
A firearms incident was declared and armed officers were deployed by the Met Police.
Officers found a 50-year-old woman who had sustained minor facial injuries believed to be from a shotgun pellet. London Ambulance Service attended but the woman did not require hospital treatment.
Following the incident, authorisation has been given for a section 60 order providing officers with additional search powers. It will be in place in Thornton, Brixton Hill, Tulse Hill, Streatham Hill, Streatham Wells and Knights Hill wards until 7am on Saturday, 16 January.
A crime scene remains in place this evening while enquiries continue.