The train, which was going to Porto in Portugal from Spain's Vigo, appeared to have hit the wall of a bridge as it was going underneath, prompting it to crash just before entering a station, according to the mayor of the nearby town of O Porrino.
Authorities in the Galicia region where the accident took place said that the train conductor was one of the two Spaniards who died in the today morning accident, which also saw some 47 people hurt.
Locals gathered today evening at the scene of the accident -- where a carriage of the train still lay on its side, the front completely caved in and mangled -- questioning why the crash happened on a good-visibility, straight line.
Adif, the company in charge of railway tracks in Spain, said that routine maintenance work was being conducted in the area.
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This was confirmed by Rafael Catala, acting Public Works Minister, who said it meant "that trains are provisionally diverted to another track, forcing them to reduce their speed according to regulations".
Maria del Carmen Perez, who lives in front of the scene of the accident, said the trains that make the Vigo to Porto connection "go by so fast that the windows of my house almost tremble".
Like several others, Ramon Gonzalez, a man interviewed by Spanish television who works in the station cafeteria near the accident, pointed out that the tracks were in a straight line.
"The train was due to stop in 50 metres, so this isn't normal," he said.
Alex Ramilo, a 15-year-old local resident who was biking over the bridge when the crash happened, told AFP he heard a "deafening noise."
"I looked and saw the train derailing. I was speechless, in shock, I didn't really realise what had happened," he said.