A property in Borough Market has been evacuated because of "an unidentified substance" delivered in an envelope, the Metropolitan Police have confirmed.
The property has been evacuated as a precaution, and three people have been treated for minor injuries.
Witnesses at the scene posted pictures on social media, which appears to show officials congregated around the Feng Sushi restaurant towards the back of the market.
The Met said police, London Ambulance Service and London Fire Brigade are in attendance at the scene near London Bridge.
Officers also confirmed to the Daily Star they were dealing with a "chemical incident," and there has been speculation about an acid attack.
A crime scene is in place, and no arrests have yet been made. A statement from the Met says that "at this early stage this is not being treated as a terror-related incident."
Just two months ago Borough Market was the scene of terror when a van drove into pedestrians on London Bridge before three people got out and began stabbing people with long knives.
Eight people were killed in the attack, which followed similarly high-profile atrocities in Westminster and Manchester.