At least 78 people have been killed in the passenger train derailment in north-western Spain, officials say.
More than 140 were hurt, 20 seriously, after all eight carriages of the Madrid to Ferrol train came off the tracks near Santiago de Compostela.
Media reports say the train may have been travelling at more than twice the speed limit around a curve.
It is the worst train crash in Spain in 40 years. Seven days of mourning have been declared in the Galicia region.
Prime Minister Mariano Rajoy, who was born in Santiago de Compostela, has arrived at the scene of the accident.
The black box of the train is now with the judge in charge of the investigation.
Spain's last major rail disaster was in 1972 when 77 people were killed in a derailment in Andalusia in the south.
Spain generally has a relatively good record in terms of rail safety, says the BBC's Tom Burridge in Madrid.
This is a country which has invested huge amounts of money in its rail network, he says.
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