A man was taken to hospital after being sprayed in the face with a liquid substance in Surbiton.
Police were first called to the junction of Brighton Road and Portsmouth Road at 4.10pm on January 19 along with ambulance and fire crews.
Initial tests identified the substance as less dangerous than ammonia and CCTV is being examined.
The man has been discharged from hospital following treatment.
No arrests have been made.
Any witnesses or those with further information are urged to call 101 quoting reference number CAD 4727/20Jan.
A spokesperson for London Fire Brigade said: “Firefighters were called at 1615 on Friday to an incident on Portsmouth Road in Surbiton.
“A crew assisted London Ambulance Service crews by treating a man at the scene before he was taken to hospital.
“A fire engine from Surbiton Fire Station attended the scene.”
A spokesperson for Kingston Police said: “#APPEAL for witnesses “Police were called at around 16:10hrs on Friday, 19 January, to reports of a man sprayed with a liquid substance at the junction of Brighton Road and Portsmouth Road in Surbiton.
“Officers attended along with LAS and LFB. The man was taken to hospital and has been discharged.
“There has been no arrest at this stage.
“We are pleased that the man has been discharged from hospital following treatment and detectives from the Met’s South West CID are investigating.
“Their investigation will utilise all available tactics, including analysis of CCTV and of the liquid, which initial tests indicate is a less harmful substance than ammonia.
“Any witnesses or anyone with information or dashcam footage is asked to call 101, ref CAD 4727/20jan, or to remain anonymous contact Crimestoppers.”
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