Madrid: Two days after Spain suffered its deadliest rail disaster in decades - which killed 80 people and maimed scores of others - one question surpassed all others -Why was the train moving so fast?
The derailment sent pieces of the sleek train plowing across the ground in a ghastly jumble of smashed metal, dirt and smoke.
Investigators opened a probe on Thursday into possible failings by the 52-year-old driver and the train's in-built speed-regulation systems.
Experts said one, or both, must be at fault for the disastrous Wednesday night crash of the train that was carrying 218 passengers and five crew members to Santiago de Compostela, a destination of Catholic pilgrimage preparing to celebrate its most revered saint.
Police has taken the driver of a Spanish train into custody in hospital after at least 80 people died when it derailed and caught fire in a dramatic accident which an official source said was caused by excessive speed.
The eight-carriage high velocity train came off the tracks just outside the pilgrimage centre of Santiago de Compostela in northwestern Spain on Wednesday night. It was one of Europe's worst rail disasters.
The source had knowledge of the official investigation into a crash which brought misery to Santiago on Thursday, the day when it should have celebrated one of Europe's biggest Christian festivals. Authorities cancelled festivities as the city went into mourning.
The Galicia region supreme court said in a statement that the judge investigating the accident had ordered police to put the driver in custody and take a statement from him. He was under formal investigation, the court said.
Dramatic video footage from a security camera showed the train, with 247 people on board, hurtling into a concrete wall at the side of the track as carriages jack-knifed and the engine overturned.
One local official described the aftermath of the crash as like a scene from hell, with bodies strewn next to the tracks.
The impact was so huge one carriage flew several metres into the air and landed on the other side of the high concrete barrier.
Some 94 people were injured, of whom 35 were in a serious condition, including four children, the deputy head of the regional government said.
"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, said.
The train had two drivers, the Galicia government said, but it was not immediately clear which one was in hospital and under investigation.
The 52-year-old had been a train driver for 30 years, a Renfe spokeswoman said. Many newspapers published excerpts from his Facebook account where he was reported to have boasted of driving trains at high speed. The page was taken offline on Thursday and the reports could not be verified.
El Pais newspaper said one of the drivers told the railway station by radio after being trapped in his cabin that the train entered the bend at 190 kilometres per hour (120 mph). An official source said the speed limit on that stretch of twin track, laid in 2011, was 80 kph.
"We're only human! We're only human!" the driver 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."
Investigators were trying to urgently establish why the train was going so fast and why security devices to keep speed within permitted limits had not worked.
The train, operated by state-owned company Renfe, was built by Bombardier and Talgo and was around five years old. It had almost the maximum number of passengers.
Spain's rail safety record is better than the European average, ranking 18th out of 27 countries in terms of railway deaths per kilometres travelled, the European Railway Agency said. There were 218 train accidents in Spain between 2008-2011, well below the European Union average of 426 for the same period, the agency said.
Firefighters called off a strike to help with the disaster, while hospital staff, many operating on reduced salaries because of spending cuts in recession-hit Spain, worked overtime to tend the injured.
The disaster happened at 8.41 pm (1841 GMT) on the eve of a festival dedicated to St James, one of Jesus's 12 disciples, whose remains are said to rest in the city's centuries-old cathedral.
The apostle's shrine is the destination of the famous El Camino de Santiago pilgrimage across the Pyrenees, which has been followed by Christians since the Middle Ages.
One US citizen died in the crash and five were injured, the State Department said in Washington. Mexico said one of its nationals was among the dead.
At least one British citizen was injured, a British embassy spokesman said. Several other nationalities were believed to be among the passengers.
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.
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 disaster.
King Juan Carlos and Queen Sofia also went to Santiago and visited the injured in hospital.
Passenger Ricardo Montesco told Cadena Ser radio station the train approached the curve at high speed, twisted and the carriages piled up one on top of the other.
Both Renfe and state-owned Adif, which is in charge of the tracks, had opened an investigation into the cause of the derailment, Renfe said.
Clinics in Santiago de Compostela were overwhelmed with people flocking to give blood, while hotels organised free rooms for relatives. Madrid sent forensic scientists and hospital staff to the scene on special flights.
The train was travelling from Madrid to Ferrol on the Galician coast when it derailed, Renfe said in a statement. It left Madrid on time and was travelling on schedule, a spokeswoman said.
With Reuters input
Spain train crash: Galicia derailment kills 78
At least 78 people have been killed in the passenger train derailment in north-western Spain on Wednesday.
More than 140 were hurt, 36 seriously, after all eight carriages of the Madrid to Ferrol train came off the tracks near Santiago de Compostela.
Media reports say the train may have been travelling at more than twice the speed limit around a curve.
Officials say one of the train's drivers has been put under formal investigation.
It is one of Spain's worst ever train crashes. PM Mariano Rajoy has declared three days of national mourning.
"Today is a very difficult day. Today we have lived through a terrible, dramatic accident, which I fear will stay with us for a long time.
"For someone from Santiago, like myself, believe me, this is the saddest Day of Saint James of my life."
Two investigations are being carried out - one judicial, the other by the investigative commission for rail accidents, under the Ministry of Public Works, Mr Rajoy added.Continue reading the main story
Mr Rajoy, who was born in Santiago de Compostela, has been visiting the scene of the accident.
"I want to express my affection and solidarity with the victims of the terrible train accident in Santiago," Mr Rajoy said earlier.
The black box of the train is now with the judge in charge of the investigation.
The president of railway firm Renfe, Julio Gomez Pomar, has said the train in the crash had no technical problems.
"The train had passed an inspection that same morning. Those trains are inspected every 7,500km... Its maintenance record was perfect," he told Spanish radio.
Spain generally has a relatively good record in terms of rail safety, says the BBC's Tom Burridge in Madrid.
This is a country which has invested huge amounts of money in its rail network, he says.
According to official figures, the crash is one of the worst rail disasters in Spanish history.
In 1972, a frontal train crash in Andalusia, in the south of the country, left dozens of people dead. The figures given at the time range between 76 and 86.
In 1944, hundreds of people were believed to have been killed in a crash in Torre del Bierzo, in Leon province - though the official account in days of heavy censorship under Gen Francisco Franco gave the figure as 78 killed.
Renfe said the train came off the tracks on a bend about 3 or 4km (2-2.5 miles) from Santiago de Compostela station at 20:41 local time (18:41 GMT) on Wednesday.
It was on the express route between the capital, Madrid, and the ship-building city of Ferrol on the Galician coast, with 218 passengers on board - in addition to an unknown number of crew members.
Firefighter Jaime Tizon, one of the first to reach the site of the crash, described the scene as "hell".
"I'm coming from hell, I couldn't tell you if the engine was on fire, or one of the carriages or what..." he told ABC after dragging the injured and bodies from the train.
Earlier, the leader of the regional government Alberto Nunez Feijoo described it as "a Dante-esque scene", in comments to Spanish radio.
One witness, Ricardo Montesco, described how the train carriages "piled on top of one another" after the train hit a curve.
"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 told Spanish Cadena Ser radio station.
Several eyewitnesses described the train travelling very fast before it derailed.Too fast?
Renfe says it and the track operating company Adif are collaborating with a judge appointed to investigate the accident.
One of the drivers who was trapped in the cab of the train after the accident is quoted as saying moments after the crash that the train had taken the curve at 190 km/h (118mph) when entering the curve, unidentified investigation sources have told Spanish media.
The speed limit on that section of track is 80km/h.
"I hope no one died because it will weigh on my conscience," he said.
UK Foreign Secretary William Hague has said one British citizen was known to have been injured in the accident.
The derailment happened on the eve of Santiago de Compostela's main annual festival where thousands of Christian pilgrims were expected to flock to the city in honour of Saint James.
The city's tourism board said all festivities planned for Thursday have been cancelled.