The Metropolitan Police said they had been called to reports of a collision on Lavender Hill, near London's busy Clapham Junction train station.
"The driver has been taken to a south London hospital. A number of passengers were treated by LAS (London Ambulance Service) at the scene," police said in a statement.
"Two passengers remain trapped on the upper deck. The road is currently closed to traffic."
(Reporting by Alistair Smout, editing by Estelle Shirbon)
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)