Leaked audio recordings that were published in Spanish media have revealed conversations between train drivers and a control centre just minutes before a deadly crash on Wednesday morning, that has killed 69 people.
Officials are investigating the cause of the disaster, which occurred when a train from Madrid to Seville barrelled into a stationary train near Urda.
Three audio recordings between Madrid's control centre and two train drivers appear to show that one high-speed train was given clearance to move even though another train had stalled on the track, about 25km (15 miles) ahead.
Prime Minister Pedro Sánchez has said that authorities will "get to the bottom of every last detail of this tragedy".
Dozens of people were injured, with survivors recounting harrowing scenes people crying and bleeding, passengers trapped in their seats, missing limbs and smoke billowing throughout the carriages, one of which caught fire.
On Thursday, Spain's King Felipe VI and Queen Letizia visited some of the injured passengers in a hospital in Toledo.
He later expressed condolences to the victims' relatives, pledging that the investigation would determine why the crash happened, and what measures would be taken for this not to happen again.
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