The driver of a train that derailed in north-western Spain, killing at least 80 people, is under police guard in hospital amid reports the crash was caused by excessive speed.
The eight-carriage high speed train came off the tracks just outside the pilgrimage centre of Santiago de Compostela on Wednesday night in one of Europe's worst rail disasters.
The High Court in Galicia says Francisco Jose Garzon, who sustained minor injuries, has been placed under surveillance and will be questioned by police. It says no arrest had been ordered at this stage, AFP reports.
Ninety-four people remain in hospital with the condition of 35, including four children, in a serious condition.
A spokesperson for state train operator, Renfe, said the 52-year-old had been a train driver for 30 years. The cause of the crash is not yet known, but it has been widely reported the train was travelling well in excess of the 80km/h speed limit.
Security camera footage showed the train with 247 people on board hurtling into a concrete wall at the side of the track as carriages jack-knifed and the engine overturned.
One local official described the aftermath of the crash, on the eve of one of Europe's biggest Christian festivals, as like a scene from hell, with bodies strewn next to the tracks.
The impact was so huge one carriage flew several metres into the air and landed on the other side of the high concrete barrier, Reuters reports.
Investigators were trying to urgently establish why the train was going so fast and why failsafe security devices to keep speed within permitted limits had not worked.
El Pais newspaper said one of the two drivers on board told the railway station by radio that the train entered a bend at 190km/h, twice the permitted speed.
Newspaper accounts cited witnesses as saying that one driver Francisco Jose Garzon, who had helped rescue victims, shouted into a phone: "I've derailed! What do I do?". Many newspapers published excerpts from his Facebook account where he was reported to have boasted of driving trains at high speed. The page was taken offline on Thursday and the reports could not be verified.
The disaster happened at 8.41pm on Wednesday, the eve of a festival dedicated to St James, one of Jesus' disciples, whose remains are said to rest in the city's centuries-old cathedral.
Prime Minister Mariano Rajoy, who was born in Santiago de Compostela, the capital of Galicia region, visited the site and the main hospital on Thursday. He said two inquiries into the crash have begun and declared three days of official national mourning for the victims.
King Juan Carlos said all Spanish people share the pain of the families and friends of those killed and praised the "spirit of citizenship" shown by rescue workers and blood donors.