SANTIAGO DE COMPOSTELA, Spain (CNN) -- The crumpled wreckage of eight train cars sent careering onto their sides when a train derailed in northwestern Spain has now been removed from the tracks, but the grim task of identifying the dead continued Friday.
Investigations into the cause of the crash are still under way, but suggestions that the train was traveling too fast have come to the fore.
The crash on the outskirts of Santiago de Compostela, a city popular with tourists and Christian pilgrims, late Wednesday shocked the Galician region and the nation.
A spokeswoman for the Galician regional government told CNN that at least 78 people are confirmed dead but that the number could rise to 80. Of the dead, 72 have been identified, she said.
A spokeswoman for the department of health in the Galicia region said 81 people are still being treated in hospitals, 31 of them in a critical condition. Of those 31, three are children.
Those hospitalized include 31 from Galicia, 38 from other Spanish regions and eight from Argentina, Colombia, Peru, the United States and Britain. The nationalities of four others have not been established.
An American woman named as Ana-Maria Cordoba from Arlington, Virginia, is among the dead. And at least five other U.S. citizens were injured, Deputy State Department spokeswoman Marie Harf said.
The unidentified remains will be sent for DNA testing in Madrid, police Superintendent Antonio del Amo said at a news conference Friday. The process could take days or even weeks, he said.
Conflicting accounts have emerged in the past two days over the number of people killed and injured. Del Amo explained the confusion by pointing out that the operation was very complex and involved a difficult accident scene.
Galicia police Chief Jaime Iglesias on Friday confirmed that the train driver is under police detention because of "a crime."
When asked the follow-up question, "What crime?" he responded: "Well ... in connection to the accident, in connection with his recklessness, in connection with causing the accident."
Investigators were expected to ask the train driver more questions Friday.
Maria Pardo Rios, a spokeswoman for the Galicia regional supreme court, said Thursday that the driver was under formal investigation. "He is not being charged by a judge at the moment -- it is all at a police level," she said.
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, and that the limit on a curve was 80 kilometers per hour (50 mph).
National daily newspaper El Mundo published a front page picture of a man said to be the driver, his face bloodied, making a cell phone call after the crash.
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 for that 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 it derailed at 8:41 p.m. Wednesday, the state railway said.
'We cry for the victims'
Workers were using a large crane to remove the train's two engines, one at the front and the other at the rear, from the track Friday morning.
Security footage revealed how the train hurtled round a bend before its cars derailed and slammed on their sides into a concrete support structure for a bridge. The impact also overturned the front engine.
Flames burst out of one train car as another car was snapped in half after the crash. Rescue crews and fellow passengers pulled bodies through broken windows and pried open doors as stunned survivors looked on.
Spain's King Juan Carlos and his wife, Queen Sofia, visited a hospital in Santiago de Compostela on Thursday evening to meet some of those who were injured.
"All Spaniards, we are united at this time. ... Really all Spaniards join in the pain of the families of the dead," he said. "We hope that the wounded will recover, little by little."
The royal family canceled all events scheduled for the day out of respect for the day of mourning, the royal household told CNN.
Alberto Nunez Feijoo, head of the regional government in Galicia, declared seven days of mourning in the region for victims of the tragedy.
In a speech, he said "all of the community cries about the tragedy that we are living, we cry for the victims, we cry for the unease and sadness of the families."
Spanish Prime Minister Mariano Rajoy viewed the scene of devastation and visited some of the hospitalized crash victims Thursday.
Rajoy, who is from Santiago de Compostela, said two investigations are under way. "We want to establish what happened," he said.
The prime minister declared three days of national mourning to honor the victims of the crash.
The crash 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.
Victim: 'Everything went dark'
One 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.
Through the darkness, passenger Stephen Ward saw a little circle of light -- the door of the train.
Rescuers came through it and helped the 18-year-old from Bountiful, Utah, get out.
He waited for hours while victims with more serious injuries were taken to the hospital. As he watched rescue crews carry the dead and wounded, he cried and sang church hymns to calm himself down.
A photo taken at the scene shows him leaning on a police officer as he walks beside the tracks, with blood oozing down his face and splattered on his crisp, white shirt.
The Mormon missionary walked past dead bodies on the ground. He told London's Daily Telegraph that it looked like a scene from hell.
U.S. citizen among those killed
When the train crashed, Ana-Maria Cordoba was on the way with her husband and their daughter to visit her son, who had been on a pilgrimage in Spain, the Catholic Diocese of Arlington told CNN.
Cordoba, who worked for the diocese, was killed, spokesman Michael Donahue said.
Her husband and daughter are hospitalized in stable condition, the diocese said.
CNN's Houston affiliate KHOU named a couple from the Texas city, Robert and Myrta Fariza, as also being among the injured Americans.
According to an image it published of a note apparently posted on the door of their home, Myrta Fariza is in critical condition. Her husband was also injured but is "recovering well," it said.
Interim charge d'affaires Luis G. Moreno at the U.S. Embassy in Madrid said it was in touch "with families of some injured American citizens."
A British citizen was also among the injured, UK Foreign Secretary William Hague said.
The state rail company, RENFE, stated that 218 passengers were on the manifest. It's not clear how many crew and staff were aboard the train.
-- CNN's Al Goodman reported from Santiago de Compostela and Laura Perez Maestro from Galicia. CNN's Laura Smith-Spark wrote in London. CNN's Jonathan Helman, Catherine E. Shoichet, Elwyn Lopez, Patrick Sung, Eric Marrapodi, Jill Dougherty, Nelson Quinones, Marysabel Huston-Crespo, Mariano Castillo and David Valenzuela contributed to this report.
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