Six people have been injured after a noxious substance was thrown during an incident at Westfield shopping mall in east London.
A 15-year-old boy has been arrested on suspicion of causing grievous bodily harm in connection with the incident on Saturday evening.
Three of the victims needed hospital treatment after they were hit with the substance during an “altercation” between two groups of males at the Stratford centre.
Onlookers reported scenes of panic in the aftermath of the incident which was first feared to be a series of random attacks.
One witness described seeing a young male victim screaming in pain as his friends shouted “it is an acid attack, he is burning”, while others rushed to wash the substance from their skin.
Scotland Yard said the altercation took place inside the shopping centre shortly before 8pm.
“During this incident a noxious substance was thrown. When the liquid was thrown, both groups ran from the scene,” the force said.
One witness, Imran Tahir Rizvi, said he overheard the friends of one victim, aged 18 or 19, shouting about an “acid attack”, then saw a young man lying on the floor screaming of a burning pain.
“(They were) screaming and shouting for help as he was feeling a burning sensation on his skin,” Rizvi said.
“His fellows were shouting at police for something. Initially people thought it was a fight. But the guys (with) the victim started shouting ‘it is an acid attack, he is burning’.”
A man who gave his name as Hossen, 28, a Burger King assistant manager, said he saw a victim and his friend, a known local homeless man, run into the restaurant’s bathroom “to wash acid off his face”.
“There were cuts around his eyes and he was trying to chuck water into them,” he said.
Members of the London ambulance service hazardous area response team arrived at the scene after the alarm was raised.
In a video shot by Rizvi, a man could be seen sitting down “crying (and) shouting in pain “ while surrounded by paramedics.
Paul Gibson, London ambulance assistant director of operations, said teams arrived within 10 minutes of the first emergency call and provided fist aid with help from the police and London fire brigade.
“We treated six patients in total and took three to London hospitals,” he said. Scotland Yard said all the victims were male and inquiries are ongoing into the incident.
Chief superintendent Ade Adelekan, Newham borough commander, said: “I would like to be very clear concerning this incident. What initially may have been perceived as a number of random attacks has, on closer inspection, been found to be one incident involving two groups of males.”
A significant rise in acid attacks in the UK has prompted calls in recent months to restrict the sale of corrosive substances which can be bought easily over the counter.