Police were called to the scene at about 8pm on “reports of a group of males spraying what is believed to be a noxious substance,” the Metropolitan Police said in a statement.

One man has been arrested on suspicion of grievous bodily harm. The incident is not being treated as terror-related, however.

“A number of people have been reported injured at different locations - believed to be six people. We await further details,” the police said. "Officers remain on the scene. A cordon is in place. Enquiries continue."

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Videos shared on social media appear to show victims being treated for their injuries inside the train station, which is located next to the shopping centre.

London Ambulance Service and London Fire Brigade are at the scene.