Black box recordings revealed that the train was travelling at 192kph (119mph) when the brake was applied; the train derailed at 153kph. The speed limit at the spot where the train derailed was set at 80kph an hour.
"Seconds before the accident the brakes were activated. It is estimated that at the time of the derailment the train was travelling at 153 kilometres an hour," the High Court of Galicia which is leading the investigation said.
The driver of the train was speaking on his work phone at the time of the accident and appeared to consult a map or other document, the court added in a statement.
"Minutes before the train came off the tracks he received a call on his work phone to get indications on the route he had to take to get to Ferrol.
From the content of the conversation and background noise it seems that the driver consulted a map or paper document," it said.
The eight-carriage train was travelling from Madrid to Ferrol on Spain's northwestern coast when it flew off the tracks last Wednesday on a bend and ploughed into a concrete siding about four kilometres (2.5 miles) from the pilgrimage city of Santiago de Compostela.
Examining judge Luis Alaez on Sunday charged the driver, Francisco Jose Garzon Amo, 52, with 79 counts of reckless homicide and released him under court supervision.
The train had two data recording "block boxes" which were analysed for the first time by police on Tuesday in the presence of the examining judge.
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 had no technical problems and had just passed an inspection on the morning of the accident, Renfe said.
The train's data recorders also appear to show the driver consulting a map at the time of the accident.
"Minutes before the train came off the tracks he received a call on his work phone to get indications on the route he had to take to get to Ferrol. From the content of the conversation and background noise it seems that the driver consulted a map or paper document," a court statement said.
Garzon, 52, admitted during his court appearance Sunday that he had had a "lapse" of concentration, Spanish media have 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 wrote.
State railway track operator Adif is checking all tracks and security systems in its network in the wake of the accident, a company spokeswoman said.
"This is a precautionary measure. After what happened, the protocol is to review all systems to confirm that everything is working properly," she said.
The train was on a route that uses both high-speed and conventional track.
On the high-speed sections a sophisticated security system automatically slows down trains that are going too fast.
The accident happened on a conventional section of the track where the older security system in place only automatically stops trains going above 200 kph and it is up to the driver to respond to prompts to slow down.
The driver had complained in the past about the security system in place at the spot of the accident did not automatically brake all speeding trains, a spokesman for the Galician branch of train drivers union Semaf said.
"He himself had said that it was incredible that speed was not controlled at this spot, that you could not go directly from 200 kph to 80 kph without the supervision of any security system," the spokesman, Rafael Rico, told AFP.
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.
Sixty-six people caught up in the crash were still in hospital on Tuesday, 15 of them critically including one child, regional health authorities said.