Six people have been injured in a suspected noxious substance attack at an east London shopping centre.
The incident was not being treated as terror-related, a police spokesman said.
Scotland Yard said officers were called shortly before 8pm on Saturday to the area around Stratford Centre, opposite the Westfield shopping centre, amid reports of a group of men spraying what is believed to be a noxious substance.
One man has been arrested on suspicion of causing grievous bodily harm.
Witnesses reported scenes of panic in the immediate aftermath of the incident, with victims rushing to clean their wounds with water.
Police immediately put a cordon at the front of the shopping centre, with a handful of young witnesses visibly shaken by what they saw.
One said: "I can't speak now, my mate's been hurt."
Police at the scene described it as an acid attack.
Witnesses said it was happened after an argument broke out among a group of people.
A man who gave his name as Hossen, 28, a Burger King assistant manager, told the Press Association he saw a victim and his friend, a known local homeless man, run into the fast food outlet bathroom "to wash acid off his face".
He said: "There were cuts around his eyes and he was trying to chuck water into them."
Inside the Burger King toilets, water could be seen all over the floor, along with toilet tissue and medical gloves.
Outside, people gathered at police cordons while victims were being treated behind a blue screen.
London Ambulance Service paramedics and the London Fire Brigade also attended as a number of victims were reported at different locations within the centre, with the number affected believed to be six people.