The driver of a train that derailed in northwestern Spain, killing at least 78 people, is under detention and is being investigated for "a crime," the regional police chief said 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.
Police are guarding the hospital bed where the driver was placed in detention Thursday afternoon, Maria Pardo Rios, a spokeswoman for the Galicia regional supreme court, told CNN.
Investigators are expected to ask the train driver, who is under formal investigation, more questions on Friday. The case has not yet been turned over by police to judicial authorities, she said.
Galicia regional police chief Jaime Iglesias on Friday confirmed that the driver is under police detention because of "a crime."
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."
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.
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.
A spokeswoman for the Galician regional government told CNN at least 78 people are confirmed dead and 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 identified as Ana-Maria Cordoba from Arlington, Virginia, is among the dead. And at least five other U.S. citizens were injured, said State Department deputy spokeswoman Marie Harf.
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.
Questions over train's speed
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.
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.
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.
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.
Survivor: We looked like the walking dead
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.
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.