Three people have been treated for minor injuries after an 'unidentified substance' was delivered in an envelope to a sushi restaurant in London Borough Market.

The Metropolitan Police said the incident is not being treated as terror-related 'at this early stage'.

Officers were called to Feng Sushi at 1.38pm on Thursday and no arrests have been made.

London Fire Brigade said firefighters using protective equipment were inside the building after they were called to assist police with a 'chemical incident'. 'A community warden then told me that a white powder had been received,' Mr Dawson added.

'I asked him for where he heard that and he couldn't say.

'Police on the scene didn't confirm anything. And Borough Market security said "some kind of corrosive material attack or incident".' 

The property in Stoney Street - one of the locations targeted by the London Bridge terrorists in June - was evacuated and a crime scene put in place.

London Ambulance Service said three people were treated at the scene and 'no one was taken to hospital'.