A girl aged 12 has been sprayed in the face with a substance police believe may have been antifreeze.
The incident happened outside a branch of Asda in, Tranent, East Lothian, between 3.45pm and 4pm on Friday.
She was sprayed with the substance by one of a group of four males while walking with her friend.
They are described as around 16 and all wearing hoodies.
While she was uninjured, her clothes were discoloured and police are now appealing for witnesses of the incident.
Detective Constable Mandy Cummings 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.