A murder investigation has been launched after the death of a woman who suffered serious burns when she was sprayed with a chemical.
Joanne Rand, 47, from Marlow, Buckinghamshire, was sitting on a bench in Frogmoor, High Wycombe, on Saturday June 3 when a fight broke out nearby.
She was sprayed with a liquid, believed to be an alkaline substance, after a bottle was kicked during the altercation.
She was taken to hospital for treatment and later discharged but she was readmitted to Stoke Mandeville Hospital on Friday, where she died the following Wednesday.
A Thames Valley Police spokesman said a post-mortem examination would be carried out to establish an exact cause of death.
The force has released a picture of the bottle which has not yet been found.
Detective Superintendent Paul Hayles said: "A team of detectives is continuing to investigate this incident and carry out enquiries.
"I would like to appeal to the public, particularly those who live or work between Frogmoor and the railway station in High Wycombe, to be aware of the bottle photographed which may have been discarded possibly in or with a dark coloured shoulder bag in the area.
"I would like to warn members of the public not to touch the bottle if they see it but to instead contact police as soon as possible.
"The bottle is white and has an orange or red hazard label on the side."
Xeneral Webster, aged 18, of Westway, Hammersmith and Fulham, London, was charged on Tuesday with one count of robbery in connection with the incident.
He appeared at High Wycombe Magistrates' Court on Wednesday and was further remanded by the court.
An 18-year-old man, from London, was arrested on suspicion of assault occasioning GBH on Tuesday and released under investigation while police inquiries continue.