A Spanish train that hurtled off the rails and smashed into a security wall as it rounded a bend was going so fast that carriages tumbled off the tracks like dominos, killing 80 people, according to eyewitnesses and video footage.
One of the drivers of the train is now being held in custody in hospital following the horrific crash.
An analysis of video images suggests that the train may have been travelling at twice the speed limit for that stretch of track.
Spain's government said two probes have been launched into the cause of last night's crash near the Christian festival city of Santiago de Compostela in northwest Spain. The Interior Ministry raised the death toll to 80 in what was Spain's deadliest train crash in four decades, while 95 remained in hospital 36 in critical condition, among them four children.
Prime Minister Mariano Rajoy, a native of Santiago de Compostela, toured the crash scene alongside rescue workers and went to a nearby hospital to visit those wounded and their families. "For a native of Santiago, like me, this is the saddest day," said Mr Rajoy, who declared Spain would observe a three-day period of mourning. He said judicial authorities and the Public Works Ministry had launched parallel investigations into what caused the crash.
Eyewitness accounts backed by security-camera footage of the moment of disaster suggested that the eight-carriage train was going too fast as it tried to turn left underneath a road bridge. The train company Renfe said 218 passengers and five crew members were on board. Spanish officials said the speed limit on that section of track is 80 kilometres (50 miles) per hour.
An Associated Press estimate of the train's speed at the moment of impact using the time stamp of the video and the estimated distance between two pylons gives a range of 144-192 kph (89-119 mph).
Another estimate calculated on the basis of the typical distance between railroad ties gives a range of 156-182 kph (96-112 mph).
The video footage, which the Spanish railway authority Adif said probably came from one of its cameras, shows the train carriages start to buckle soon into the turn.
Murray Hughes, consultant editor of Railway Gazette International, said it appeared that a diesel-powered unit behind the lead locomotive was the first to derail. The front engine itself quickly followed, violently tipping on to its right side as it crashes into a concrete security wall and bulldozes along the ground.
In the background, all the rear carriages can be seen starting to decouple and come off the tracks. The picture goes blank as the engine appears to crash directly into the camera.
After impact, witnesses said a fire which engulfed passengers trapped in at least one carriage most likely from the diesel fuel carried in the locomotive units.
"I saw the train coming out of the bend at great speed and then there was a big noise," one eyewitness who lives beside the train line, Consuelo Domingues, told The Associated Press. "... Then everybody tried to get out of the train."
Santiago officials had been preparing for the city's internationally celebrated Catholic festival but cancelled it and took control of the city's main indoor sports arena to use as a makeshift morgue. There, relatives of the dead could be seen sobbing and embracing each other. The Interior Ministry, responsible for law and order, ruled out terrorism as a cause. Seven days mourning was declared in Galicia, the local region.
Spanish media said the train had two drivers aboard and both survived. However, Galician court officials said the train had only one driver. Court spokeswoman Maria Pardo Rios said the driver survived and was expected to give a statement to police later. She declined to name the driver but said he was not being treated as the suspect of a crime.
Renfe said it and Adif, another state-owned company that manages tracks, signals and other railway infrastructure, were co-operating with a judge appointed to investigate the accident.
Investigations into Spain's worst rail disaster in more than 40 years – which has left at least 80 people dead and more than 160 injured – are focusing on the driver after officials confirmed that excessive speed caused the train to career off the rails.