The driver of a tram which derailed killing seven people and injuring dozens more has been arrested.

Emergency services are still working at the scene near Sandilands tram stop in Croydon, south London, to free people trapped in the two-carriage vehicle.

The tram was travelling at a "significantly higher speed than is permitted", the independent Rail Accident Investigation Branch said.

More than 50 people were injured, some seriously, when the crowded rush-hour tram tipped on to its side next to an underpass near the stop shortly after 6.10am on Wednesday.

The mayor of London Sadiq Khan said that the number of dead in the Croydon tram crash "may well increase" above the five already confirmed by police.

London Fire Brigade earlier said three of the five people trapped had been rescued after they sent eight appliances and more than 70 firefighters to the scene in Addiscombe Road.

It is believed to be the first tram crash involving fatalities on board since 1959, when two women passengers and the driver died after a tram caught fire in Shettlestone Road, Glasgow, following a collision with a lorry.

British Transport Police confirmed that five people had died in the incident.

Prime Minister Theresa May said her "thoughts and prayers are with all of those who have affected by this terrible incident on the tram in Croydon".

Accident investigators have gone to the scene to probe how the derailment happened.

London Ambulance Service said: "We have treated a number of patients and over 50 have been taken to hospital."

London Fire Brigade sent eight fire engines and more than 70 firefighters to the scene at Addiscombe Road.

Station manager Joe Kenny said: "Firefighters have released a number of people and two people remain trapped.

"All the emergency services are working closely together to help those involved in this incident."

People living nearby told of hearing a loud noise and seeing the injured being carried off on stretchers.

Croydon resident Hannah Collier, 23, said: "I heard a massive crash at about 6.15am, then heard shouting, then the emergency services arrived.

"They started bringing up the casualties, some very seriously injured. People were carried away on stretchers."

A Transport for London (TfL) spokesman said: "We are currently working with the emergency services following a derailment involving a tram in Croydon.

"There is currently no service on the tram between Reeves Corner and Addington Village / Harrington Road. We will give further information as soon as possible."