Story highlights Forensic experts must carry out DNA tests on body parts to see who they belong to

The judge has until Sunday evening to decide whether to press formal charges

Interior Minister says police have accused the train driver of "reckless homicide"

At least 78 people died in the train crash near Santiago de Compostela in Galicia

Police in Spain have accused the driver of a train that derailed in northwestern Spain, killing at least 78 people, of "reckless homicide," the country's interior minister said Saturday.

The judge has until Sunday evening local time to decide whether to press formal charges against Francisco Jose Garzon, Interior Minister Jorge Fernandez Diaz told reporters in Santiago de Compostela.

The driver, who spent the past two days under detention in hospital, guarded by police, is now at the police headquarters, he said.

The data recorders from the train are still with police, he added.

Separately, a spokesman for the Galician regional Supreme Court told CNN Saturday morning that the judge had not yet questioned Garzon.

Questions have focused on the speed at which the train was traveling as it entered a curve in the track near Santiago de Compostela on Wednesday evening.

The crash on the outskirts of the city, which is popular with tourists and Christian pilgrims and was preparing to celebrate a saint's day Thursday, shocked the Galician region and the nation.

Fernandez Diaz told reporters earlier Saturday there are "rational indications" that the accident is the fault of the driver. Pressed on what those indications are, he declined to give more details.

The driver is not scheduled to appear in court Saturday. But a statement from a regional court said, "The intention, if it is possible, is that he makes an appearance in the courts."

Galicia regional police chief Jaime Iglesias told reporters Friday that the driver was under police detention because of "a crime."

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Asked what crime, he responded: "Well ... in connection to the accident, in connection with his recklessness, in connection with causing the accident."

The crumpled wreckage of the eight train cars sent careering onto their sides when the train derailed has now been removed from the tracks, but the grim task of identifying the dead continues.

Maria Pardo Rios, a spokeswoman for the Galicia regional supreme court, told CNN late Friday that 75 victims had been identified from at least 78 people killed.

At least 63 of the dead are Spanish, she said. Also among them is one U.S. citizen, Ana-Maria Cordoba from Arlington, Virginia, and a number of people from Europe and Latin America.

As they are identified, most of the bodies are being returned to their grieving families, a statement from the regional justice department said. DNA testing is to be done on some remains to establish their identity and to how many people they belong, it said.

Police forensic experts said at a news conference Saturday that there are 37 body parts that must still be tested to see whether they belong to bodies that have already been identified, or to others not yet known.

About 80 people who were injured in the crash remained in hospital Saturday, about a third of them still listed in critical condition.

At least five U.S. citizens were injured, said State Department deputy spokeswoman Marie Harf.

Local newspaper La Voz de Galicia said that a funeral service for the victims would be held on Monday evening in the cathedral in Santiago de Compostela.

Going too fast?

Spanish news agency Efe and national daily El Pais cited sources within the investigation as saying that the driver had said the train was traveling about 190 kilometers per hour (120 mph).

Elena Garcia, a spokeswoman for national railway Renfe, on Friday did not disclose the speed the train was traveling on an express track, where cars can move as fast as 250 kph. She did say, though, the speed limit for the bend of track where the crash occurred is 80 kph.

Rafael Catala, secretary of state for transport and housing, told Spanish radio network Cadena SER that the "tragedy appears to be linked to the train going too fast," but that the reasons it was going so fast are not yet known.

The express passenger service was nearing the end of a six-hour trip from Madrid to the town of Ferrol in northwest Spain when the crash occurred, the state railway said.

Security footage revealed how, as the train hurtled around a bend, its cars derailed and slammed on their sides into a concrete support structure for a bridge.

Flames burst out of one train car as another car was snapped in half in the crash. Rescue crews and fellow passengers pulled bodies through broken windows and pried open doors as stunned survivors looked on.

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Maria Vigo, whose home is on the bank above the rail tracks, told CNN how she heard a crash, and then the deafening squeal of metal on concrete.

"When I saw the rail car flip into the air, I imagined something just horrible had happened," she said.

She and husband Suso sought to help the injured, taking bed sheets to wrap round the injured and ropes to haul the survivors off the tracks.

Firefighter Miguel Angel Bello said the first four minutes after he arrived on the scene were a desperate race against time.

He and fellow firefighters smashed windows and kicked in doors to pull out the passengers trapped inside as rail cars went up in flames.

A young girl in the wreckage called out to him. "She was under wreckage she said she wanted to get out and go home but she died," he said.

Survivor: We looked like the walking dead

Stephen Ward, an 18-year-old from Bountiful, Utah, who is in Spain serving on a Mormon religious mission, was one of the lucky ones.

Still patched up and wearing a neck brace, he told CNN's "New Day" show of his ordeal -- and his relief that he made it out alive and without permanent injury.

Ward blacked out when the car he was in slammed on to its side, regaining consciousness only as he was being helped out of the train.

It took him a couple of minutes to grasp that what he was seeing outside was not a dream -- and that people were dead. "They were helping out other people -- there were bodies, there was screaming, there was smoke."

The survivors looked like the walking dead, he said. "I've got staples all over my scalp, I was covered in blood. They've scrubbed most of it off me now but everyone was just covered in their own blood and occasionally the blood of others. It was gruesome to say the least."

Another victim, speaking from a hospital bed with his arm in a sling, told CNN affiliate Atlas that it seemed like the train was going fast.

"But we didn't know what was the maximum speed, so I thought it was normal," he said, "And suddenly there was a curve, the suitcases fell, and everything went dark. And I hit my head a ton of times, and 10 seconds later I was wedged between seats, and I had people's legs on top of me."

As he waited for rescuers to pull him from the wreckage, he heard other passengers yelling.

"I heard little children screaming. ... I also heard two girls that yelled out, one supporting the other," he said.

The derailment came on the eve of a public holiday to celebrate a saint's day, when more people than usual may have been traveling in the region. Planned festivities in Santiago de Compostela and across Galicia were canceled after the crash.