Police have confirmed a 16-year-old boy was taken to hospital with stab wounds after a fight broke out on Monday evening.
Officers were called to Carisbrooke Road at the junction with South Lodge Avenue in Mitcham at about 5.15pm and found the teenager with stab wounds in his arm and back.
The injured youngster was taken by ambulance to a south London hospital. His injuries are not thought to be life-threatening.
A 17-year-old man at the scene also had his jewellery and bike stolen.
Another 17-year-old man had his bike and mobile phone stolen.
They were not injured.
Police arrested a 14-year-old girl from Streatham on suspicion of robbery at 6.10pm in connection with the incident.
She has been bailed to appear in court in August.
Police enquiries continue.