Police said one of a group of four boys, all described as being aged around 16 and wearing hoodies, sprayed the substance on the 12-year-old girl’s face and clothing outside the Asda store on Haddington Road.
The incident took place between 3:45pm and 4pm on Friday, February 8th.
A police statement said that the victim was not injured but the substance did cause discolouration to her clothes. Enquiries so far suggest that the substance may have been antifreeze.
Officers are now appealing to the public for information about the incident.
Detective Constable Mandy Cummings of Dalkeith CID said: “There was no interaction between the teenagers and the victim beforehand, so this is believed to have been opportunistic and potentially thought of as a prank by those involved.
“However, this behaviour is absolutely unacceptable and this incident is being treated as an assault. Thankfully, the girl was uninjured but this understandably caused concern and upset to her and her family.
“Anyone who may have seen the teenagers in the area, or who has any information about this incident, is urged to come forward and report this.”
Those with information can call Police Scotland on 101, quoting incident number 4218 of 8th February, or contact the charity Crimestoppers anonymously on 0800 555 111.
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