The driver whose speeding train crashed, killing 78 people, is now being held on suspicion of negligent homicide, Spain's interior minister says.

Jorge Fernandez Diaz announced the step against Francisco Jose Garzon Amo, who previously had been detained on suspicion of recklessness.

The minister also says that Garzon has been discharged from the hospital and taken to a police station.

Blame has increasingly fallen on the driver, with the country's railway agency saying it was his responsibility to brake before going into the high-risk curve outside Santiago de Compostela where the train tumbled off the rails and smashed into a wall. But it's still not clear whether the brakes failed or were never used, and the driver has remained silent so far.

A blood-soaked Garzon was photographed Wednesday being escorted away from the wreckage, at first by civilians who had hurried to the scene of the accident and then by police.

Unconfirmed media reports said that Garzon had injured ribs.

In Wednesday's crash, the train's eight carriages packed with 218 passengers blazed far over the speed limit into a curve and violently tipped over. Diesel fuel powering the engine sent flames coursing through some cabins.

The president of Adif, the Spanish rail agency, said that the driver should have started slowing the train four kilometres before the dangerous bend. He said signs clearly marked this point when the driver must begin to slow.

Normally, police take a first statement that is then examined by an investigating judge who must then take testimony within 72 hours of the arrest. That deadline is Sunday.

Although that initial court hearing would be closed, it would give hints about the status of the investigation. The judge would decide whether to jail the driver as an official suspect, release him on bail, or release him without charges. If a judge finds sufficient evidence for a criminal trial, the suspect will be charged and a trial date set.