Police put the driver of a Spanish train under investigation on Thursday after at least 78 people died when it hit a sharp bend at speed and derailed near the northern city of Santiago de Compostela, in one of Europe's worse rail disasters.Dramatic video footage from a security camera published on the website of El Pais newspaper showed the train careering into a wall at the side of the track as it came off the rails on the bend on Wednesday night.Police had put the train driver under formal investigation, a spokeswoman for Galicia's Supreme Court told Reuters, without naming him.The Galicia government said the train had two drivers and one was in hospital but it was not immediately clear which driver was under investigation.Newspaper reports cited witnesses as saying driver Francisco Jose Garzon,who helped rescue victims, had shouted: "I've derailed! What do I do?" into a phone.El Pais said one of the drivers was trapped in his cabin and told the railway station by radio that the train entered the bend at 190 kilometres per hour (120 mph)."We're only human! We're only human!" he told the station, the newspaper said, citing sources close to the investigation. "I hope there are no dead, because this will fall on my conscience."The disaster happened on the eve of a major religious festival in the ancient northwestern city at 8.41 p.m. (1841 GMT) on Wednesday. Officials said several nationalities were among the 130 injured, of whom 36 including four children, were in serious condition.In what one local official described as a scene from hell, bodies covered in blankets lay strewn around the train track next to overturned carriages as smoke billowed from the wreckage and bloodied passengers staggered away.Cranes were still pulling out mangled debris on Thursday morning, 12 hours after the crash. Emergency workers had stopped their search for survivors, the court spokeswoman said.SPEEDING LIKELY CAUSEOne official source said speeding was a likely cause of the derailment, but the public works minister said it was too early to say exactly what had happened. El Pais cited sources close to the investigation as saying the train was travelling at more than twice the speed limit for the sharp curve and Santiago's mayor said the train was probably going too fast.The train driver had been sedated, said Juan Jesus Garcia, the secretary general of the Renfe train drivers union, adding he hoped to visit him on Thursday.He had been operating trains in the area for three years, Garcia said.Neighbours ran to the site to help emergency workers tend to the wounded. Ana Taboada, a 29-year-old hospital worker, was one of the first on the scene."When the dust lifted I saw corpses. I didn't make it down to the track, because I was helping the passengers that were coming up the embankment," she told Reuters. "I saw a man trying to break a window with a stone to help those inside get out.""We heard a massive noise and we went down the tracks. I helped get a few injured and bodies out of the train. I went into one of the cars but I'd rather not tell you what I saw there," Ricardo Martinez, a 47-year old baker from Santiago de Compostela, told Reuters.Prime Minister Mariano Rajoy, who was born in Santiago de Compostela, the capital of Galicia region, visited the site and the main hospital on Thursday. He declared three days of official national mourning for the victims of the disasterThe Santiago de Compostela train operated by state rail company Renfe, which had 247 people on board, derailed as the city prepared for the renowned festival of Saint James, when thousands of Christian pilgrims from across the world pack the streets.The city's tourism board said all festivities, including the traditional High Mass at the centuries-old cathedral, had been cancelled as the city went into mourning following the crash.Passenger Ricardo Montesco told Cadena Ser radio station the train approached the curve at high speed, twisted and wagons piled up one on top of the other."A lot of people were squashed on the bottom. We tried to squeeze out of the bottom of the wagons to get out and we realised the train was burning. ... I was in the second wagon and there was fire. ... I saw corpses," he said.