Nine people were injured when a pleasure boat collided with Tower Bridge on Wednesday lunchtime.
"London Coastguard is coordinating the response to an incident on the Thames in which a pleasure boat, the Millennium Diamond, was in collision with Tower Bridge," said the Maritime and Coastguard Agency.
"Several people are believed to be injured.
"Emergency services and the RNLI are on the scene."
The London Ambulance Service said it had treated nine people in connection with the incident.
The Millennium Diamond is operated by City Cruises, based at Cherry Garden Pier.
In a statement the company said: "Having made contact with the bridge, the boat continued to St. Katharine Dock with minor damage, where the river authorities, including the Port of London Authority (PLA), the police and paramedics awaited its arrival.
"City Cruises reacted quickly and continues to work with the authorities for the safety and welfare of its passengers.
" The vesselís 126 passengers and 4 crew have been disembarked at St Katharine Docks where the river authorities are currently in attendance.
"There have been a number of injuries reported, including crew who were immediately assessed and are being transferred to local hospitals."
Tower Bridge remained open to road traffic and pedestrians.
Later this month Tower Bridge celebrates its 120th anniversary.