"I'm at 190 (kmph) and I'm going to derail!" the engine driver told the controllers of RENFE, the rail network.
Two men were at the controls of the train at the time, and it was not clear who had made the call.
Police sources told Spanish newspaper El Pais that, moments after the crash, the traumatised driver made another call to the operator.
"It derailed!" he said. "What am I going to do, what am I going to do?
"We are all humans - we're humans. I hope there are no fatalities because it will all be on my conscience."
Both the drivers escaped the crash with minor injuries, but their conversations lead the interior ministry to say there was no evidence of a terrorist attack causing the crash. The speed limit for the section of the track where the accident occurred, near Santiago de Compostela, was 80 kmph (50mph).
Video cameras positioned along the track showed the train coming towards a bend, beneath a motorway, and skidding off the track. The engine seemed to remain on the rails but the middle carriages were flung from the rails and smashed into the concrete sidings beneath the bridge.
The driver told police that he had entered the bend "fuerte" (strong).
The train left Madrid's Chamartin station at 3pm on Wednesday, and should have arrived in Ferrol, on the coast of Galicia, at 10.30pm. The accident took place at 8.41pm, as the train was drawing into the station at Santiago de Compostela.
Source: The Telegraph, UK
A little too soon to confirm this report but El Pais mentions a signalling safety device that would have triggered the brakes had the train been travelling even faster at 200kph; I should have thought that with perhaps a 10% margin 90kph would have been sufficient for this location/bend.