The driver held by police after a train derailed in northwestern Spain has refused to answer questions, authorities have confirmed.
A spokesman for the National Police said the driver "has refused to answer police authorities" and added the case will now "proceed to a judicial process as soon as possible".
Francisco Jose Garzon Amo, 52, was arrested in the hospital where he is recovering after the crash which killed 78 passengers and injured another 130.
Galicia region police chief, Jaime Iglesias, earlier said Garzon would be questioned "as a suspect for a crime linked to the cause of the accident" and said he had been arrested for "recklessness".
Francisco Jose Garzon Amo pictured after the crashHe is being guarded by police in hospital, although his condition is understood not to be serious.
Pictures and video footage have emerged of him being led away from the crash scene with his head covered in blood.
The train's black box recorder has been retrieved from the wreckage near Santiago de Compostela.
Early indications suggested the train may have been travelling at more than twice the speed limit at the time of the crash on Wednesday night.
The eight-carriage train came off the tracks on a bend, hit a wall and caught fire just outside the city - a pilgrimage destination for Roman Catholics.
The train entered the bend at 190km per hour (120mph), according to local media reports. The speed limit on the curve was 80km per hour (50mph).
Mr Garzon boasted about speeding on his Facebook pageSpanish media revealed that immediately after the derailment Garzon allegedly said to officials at the railway station 3km from the crash: "I ****** up, I want to die. So many people dead, so many people dead."
El Pais newspaper quoted him as telling rail officials: "I was going at 190! I hope no one died because it will weigh on my conscience."
He is also thought to have boasted on his Facebook page about how fast he was driving a train in March last year.
The driver posted a picture of a train speedometer at 200km per hour (124mph) on the social networking site. His Facebook page has since been blocked.
There was a second driver on the train, but it is believed Garzon was the only driver at the time.
He is understood to have taken control of the train from a second driver about 65 miles (104km) south of Santiago de Compostela.
Two investigations are being carried out into the catastrophe - one to look into possible failings by the driver and the other to examine the train's in-built speed regulation systems and see if it was a technical malfunction that meant the driver was not warned of the reduced speed limit around the bend.
A truck hauls one of the damaged carriages from the scene of the crashMany questions remain unanswered about what went wrong, with some experts claiming that high speed alone would not explain the crash and speculation that the train's braking systems might have failed.
State train company Renfe said Garzon had been at the firm for 30 years and he had been driving trains for more than a decade.
He became an assistant driver in 2000 and a fully qualified driver in 2003.
Garzon is understood to have been on the Madrid to Ferrol service, on which the crash happened, for a year, after undergoing training specific to that line.
Medical experts are attempting to identify six of the 78 dead. DNA tests are expected to be carried out on those with catastrophic injuries.
Victims of the crash included a US citizen and a Mexican. At least one British citizen and four children were among the 130 people injured.
Some 31 of those in hospital are still critically ill.
Spanish newspaper El Pais has revealed details of a dramatic WhatsApp conversation between one of the survivors trapped in the train wreck and her husband.
At 8.45pm local time, the woman sent messages saying she had been in an accident and was "crushed".
Hospital staff hold a minute's silenceAfter what her husband described as "the longest five minutes of my life", she sent another message saying "I'm safe".
The 46-year-old woman escaped with minor injuries to her legs and has already been discharged from hospital.
Video footage from a security camera showed the train, which had 247 people on board, hurtling into a concrete wall at the side of the track.
The impact was so huge one carriage flew several metres into the air and landed on the other side of a concrete barrier.
The Alvia 730 series train was travelling from Madrid to the port city of Ferrol when it crashed about 8.40pm local time - 7.40pm UK time - on Wednesday.
Gonzalo Ferre, president of the rail infrastructure company Adif, said the driver should have started slowing the train 2.5 miles before reaching a dangerous bend.
People applaud after a minute's silence in Santiago de CompostelaThe crash occurred on the eve of a major Christian religious festival honouring St James, the disciple of Jesus whose remains are said to rest in a shrine.
Many of the dead or injured were believed to be Catholic pilgrims converging on the city.
Spain's Prime Minister Mariano Rajoy, who was born in Santiago de Compostela, visited the scene of the crash on Thursday and declared three days of official mourning across the country.
King Juan Carlos also visited one of the hospitals where many passengers are being treated.
The train crash is the worst Spain has experienced since a three-train accident in a tunnel in the northern Leon province in 1944.
Due to heavy censorship at the time, the exact death toll for the Torre del Bierzo disaster has never been established. The official figure was given as 78 dead, but it is thought that as many as 250 could have been killed.