Police were called at 1.38pm today to reports of an unidentified substance being delivered in an envelope to a business in Stoney Street, SE1.
Officers, London Ambulance Service and London Fire Brigade are in attendance.
The property has been evacuated as a precaution. Three people have been treated for minor injuries. A crime scene is in place. No arrests have been made.
At this early stage this is not being treated as a terror related incident