Two people are trapped and more than 50 others have been taken to hospital after a tram overturned in south London.
Police said they had been called to reports that a tram had derailed near a stop close to central Croydon, a suburb of the capital.
Pictures showed the tram lying across the tracks.
"We have treated a number of patients and over 50 have been taken to hospital," a London Ambulance spokesman said.
Eight fire engines, four specialist rescue units and more than 70 firefighters were at the scene which police described as a serious incident.
"Firefighters have released a number of people and two people remain trapped," London Fire Brigade Station Manager Jo Kenny said.
Local residents said they had heard a crash followed by shouting.
"They started bringing up the casualties, some very seriously injured. People were carried away on stretchers," Hannah Collier, 23, told Sky News.