Police are holding the engineer of the Spanish train that derailed at high speed this week on suspicion of reckless homicide.
Interior Minister Jorge Fernández Díaz said Saturday there are "reasonable grounds" to believe that Francisco José Garzón Amo is responsible for the crash that killed 78 people. But, he said, a judge is the one who will determine that.
Garzón's train is believed to have been moving at more than 190 kilometers per hour - more than twice the 80 km/h limit on a stretch of track when it derailed on a curve outside the northwestern city of Santiago de Compostela Wednesday.
Spanish police initially said they were investigating the 52-year-old driver on suspicion of recklessness. Garzón was hospitalized after the crash but has been released from the hospital and detained by police in connection with the more serious charge of reckless homicide.
The driver is expected to appear before a judge on Sunday. Spanish law requires that a judge hear a suspect within 72 hours of arrest.
Spain's state train company, Renfe, says Garzón is a 30-year company veteran who has worked as an engineer for more than a decade.
Spanish media report the driver bragged about speeding online, and that he once posted on Facebook a picture of a speedometer showing a train traveling over 200km/h. The caption for the picture, which has been deleted from the Internet, quotes Garzón as saying, "I am on the edge. I can't go faster or else I will be fined."
Spanish authorities have opened two investigations into the derailment - one by judicial authorities and another by the public works department.
Security camera footage shows the train - traveling Wednesday night from Madrid to the port of Ferrol - slamming into a concrete wall at the side of the track, its first car violently overturning.
Authorities will learn more about what happened from the data recorded by the train's "black box" data recorder, which has been recovered.
The disaster - one of the deadliest train crashes in Spanish history - happened on the eve of an annual festival dedicated to Saint James, revered as a disciple of Jesus, whose remains are said to rest in Santiago's centuries-old cathedral.
The apostle's shrine is the destination of the famous El Camino de Santiago pilgrimage across the Pyrenees, which has been followed by Christians since the Middle Ages and has had a resurgence in popularity in recent decades.