A Spanish train was hurtling around a curve at 179 kph (111 mph), more than twice the speed limit, when it leapt off the tracks in a disaster that killed 79 people, a report on the contents of the "black box" recorders showed Friday.

The train driver was on the telephone to the on-board conductor and stopped speaking just 11 seconds before the July 24 derailment near the northwestern city of Santiago de Compostela, said the report.

The driver, 52-year-old Francisco Jose Garzon Amo, has been released on bail charged with 79 counts of reckless homicide while the court runs a criminal investigation into Spain's deadliest rail accident since 1944.

"The train was running at the point of the derailment at a speed of 179 kph, the permitted speed limit being 80 kph," said the black box report released by the Galicia regional high court in Santiago de Compostela.

Two minutes before the derailment, the train was speeding down the track at 199 kph.

The recordings show the driver and conductor spoke for 1 min 40 secs, with the last words of their conversation heard exactly 11 seconds before the derailment at 8.41 pm (1841 GMT).

"At 20:41:06 the sound of the dragging of the train produced by the derailment is heard," said the report.

"At 20:41:16 the sound of dragging ends."

The on-board conductor, identified in the media as Antonio Martin Marugan, has admitted telephoning the driver to discuss which track to use in a later stop.

But the court has said the call was "normal" and the conductor was not to blame for the derailment. He is appearing only as a witness, not a suspect.

The train driver said in his first testimony to the Galicia regional court on Sunday that he "didn't understand" how he failed to brake in time, a recording of his court hearing revealed.

"I can't explain. I still don't understand," the driver told the judge when asked why he hadn't slowed down in time to take a sharp bend four kilometres (three miles) away from Santiago de Compostela.

Asked again about what caused him to crash, he added: "I tell you sincerely that I don't know. Otherwise I would not have been so crazy as not to brake" earlier.

Railway officials say the track where the train crashed was not equipped with the automatic braking systems in place on some high-speed lines and that it was therefore left up to the driver to brake.

The driver told the judge he had braked, but by the time he did so the crash was "inevitable".

"Before the train turned over, I had activated everything but I saw that no, no, it wasn't working."