Officers are on scene.
The ground is in the process of a controlled evacuation.
There are no reported injuries.
At this early stage it is believed that the object came from outside of the ground.
There have been no arrests.
We retain an open mind as to motive. Enquiries continue.
Anyone who has information concerning this incident should call officers from Lambeth by dialling 101 or call Crimestoppers anonymously on 0800 555 111.