The statement said that the driver, Francisco Jose Garzon Amo was talking on the phone to an official of national rail company Renfe when the crash happened and apparently was consulting a paper document at the time,
The preliminary probe by a Spanish court investigating the crash also said that the 54-year-old driver was travelling at 153kph almost twice the speed limit, when the crash happened last week.
According to a written statement from the court in Santiago de Compostela, driver activated the brakes "seconds before the crash."
On Sunday, Garzon was provisionally charged with 79 counts of reckless homicide.
Investigators and forensic police experts, the ministry of transport and Renfe examined the contents of the two black boxes recovered from the wrecked train.
The train was carrying 218 passengers when it hurtled off the tracks last Wednesday evening. It slammed into a concrete wall, with some of the cars catching fire.
The Spanish rail agency has said the brakes should have been applied four kilometers (2.5 miles) before the train hit the curve.
Dozens of passengers are still being treated for injuries.
(With Agency inputs)