“Detectives are investigating the circumstances that led to four people suffering serious injuries,” the Metropolitan Police said.
Two people with “less serious injuries” were treated at the scene, while the other eight were taken to hospital by ambulance.
No arrests have been made, the Met noted.
“This is an extremely upsetting incident that has left four seriously ill people in hospital,” Commander Ade Adelekan said.
“A police investigation has been launched, and will be as thorough and forensic as necessary to establish exactly what happened last night.”
He added that specialist officers will examine the scene and CCTV, but asked anyone with information to come forward.