Six people have been injured in Stratford, east London, after a reported acid attack.
Police were called to Stratford Centre, opposite Westfield, just before 20:00 BST. A man has been arrested on suspicion of grievous bodily harm.
Police said there had been reports of a group of males spraying people with a noxious substance. Ambulance and fire services were also called.
The incident is not believed to be terror related.
Those reported injured were believed to be in a number of different locations.
Six patients were treated at the scene, and three of them were taken to hospital, Paul Gibson of the London Ambulance Service said.
No-one is thought to have life-threatening or life-changing injuries.
Witnesses at the scene said an argument had broken out among a group of people.
A man who gave his name as Hossen, an assistant manager at Burger King, said a victim had run into the fast food chain to "wash acid off his face".
One man said a victim ran into a Burger King to "wash acid off his face"
The 28-year-old added: "There were cuts around his eyes and he was trying to chuck water into them."
Tahseen Taj lives in one of the buildings just opposite the shopping centre and was disturbed by the noise.
"I could hear a lot of ambulances and police from around 20:45, but also there's a West Ham match today; I thought it must be a football brawl," she said.
"But after some time it just increased and increased, and there were a lot of fire brigades and ambulances and police, and it was quite chaotic to be honest.
"I was quite worried."