Five people are trapped and 40 people have been injured after a tram overturned.
The incident, involving a two-car vehicle, happened in a tunnel in south London, a Transport for London spokesman said.
Police confirmed they were called to the scene at Sandilands tram stop in Croydon at around 6.10am.
A spokeswoman for London Fire Brigade said: "A two-car tram overturned. Five persons are confirmed trapped, and 40 persons injured."
A London Ambulance Service spokesman said: "We are attending an incident in the Croydon area and have multiple resources on way."