MADRID (AFP) - Investigators began extracting information on Tuesday from the data recording "black box" of a train that derailed in Spain, killing 79 people in the country's worst rail disaster in decades.

The information will be passed on to examining judge Luis Alaez who is leading the investigation into the causes of last Wednesday's accident near the northern city of Santiago de Compostela, a court spokesman said.

The judge on Sunday charged the driver, Francisco Jose Garzon Amo, with 79 counts of reckless homicide and released him under court supervision.

The eight-carriage train was reportedly travelling at more than double the speed limit when it flew off the tracks on a sharp bend and ploughed into a concrete siding on the outskirts of Santiago.

El Pais newspaper has reported that Garzon had told railway officials by radio that the train had taken a curve at 190 kilometres an hour - more than double the 80 kph speed limit for that section of track.

The 52-year-old admitted during his court appearance on Sunday that he had had a "lapse" of concentration, Spanish media reported.

Several newspapers said the driver told the judge he had confused the stretch of track he was on at the time of the accident with another part of the route.

"He believed he was on a different section of the track and when he started to slow down it was too late to keep control of the train," El Pais said.

State railway company Renfe has said Garzon had been with the firm for 30 years, including 13 years as a driver, and had driven trains past the spot of the accident 60 times.

The train - a model able to adapt between high-speed and normal tracks - had no technical problems and had just passed an inspection on the morning of the accident, Mr Renfe said.

The accident took place on a section of a high-speed track that can also be used by conventional trains and was not equipped with an automatic braking system in case of speeding.

Just before the spot where the accident happened, the train left a long straight stretch with a speed limit of 220 kph to enter the curve where the limit was 80 kph.