Police were called to a nature reserve in Mitcham earlier week to reports of an acid attack.
Residents said that "loads of police" and fire engines were at the scene in Longfield Drive near the roundabout near Victoria Road near midnight on August 15.
One woman said that "a young girl was attacked with acid."
A spokesman for the Met Police has now confirmed that the substance thrown in the girl's face was non-toxic.
"Police were called by London Ambulance Service at 11.37pm on Wednesday, August 15 to reports of an acid attack," he said.
"Officers, London Ambulance Service and London Fire Brigade attended the scene for minor injuries.
"An 18-year-old female was treated at the scene by LAS and LFB."
There have so far been no arrests made.
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