London (CNN)Police continued Thursday to investigate the site of a tram derailment in Croydon, south London, that killed at least seven people.
The tram’s driver, a 42-year-old man, was released on police bail early Thursday after being arrested following the crash on suspicion of manslaughter. He has not been named by the British Transport Police.
More than 50 people needed hospital treatment after the incident to the east of Croydon, a large town of about 38,000 people.
Deputy Chief Constable Adrian Hanstock said Wednesday officers who arrived on the scene shortly afterward “were met with a complex and challenging situation.”
He added: “This is a tragic incident and our hearts and thoughts go out to all those affected.”
London’s only tram network carries millions of passengers each year along 17 miles of track. Services were limited on Thursday, with no trams operating on the stretch where the derailment took place.
The overturned tram remains at the site as investigators probe what may have caused the crash. Aerial shots show that it derailed at a point where the track branches.
“We expect to be at the scene for at least the next 24 hours, continuing searches and carrying out forensic examinations in support of the investigation into the circumstances,” Hanstock said.
He said officers would assess Thursday “how and when it is appropriate to recover the tram and remove it from the tracks.”