(CNN) -- The driver of a train that derailed in northwestern Spain last week, killing 79 people, was on the phone with railway staff when the train crashed, court officials announced Tuesday, citing information from data recorders.
The train was going 153 kph (95 mph) when it derailed, the superior tribunal of Galicia said.
That's nearly twice the speed limit on the curve where the accident happened.
Authorities have charged the train's driver, Francisco Jose Garzon, with 79 counts of homicide by professional recklessness and an undetermined number of counts of causing injury by professional recklessness.
A court has granted Garzon conditional release, but his license to operate a train has been suspended for six months. He also was required to surrender his passport and report to court weekly. CNN efforts to locate him have been unsuccessful.
The train, nearing the end of a six-hour trip between Madrid and Ferrol, derailed Wednesday evening as it hurtled around a bend in Santiago de Compostela.
Minutes before the derailment, Garzon received a call on his work phone, apparently receiving instructions on the way to Ferrol from a Renfe staff member, the court said Tuesday. Background noise suggested he was looking at or shuffling papers, the court said.
On Spain's railroad system, command and control posts can communicate with drivers at any point during a journey, a spokeswoman from Renfe -- the Spanish railroad company -- told CNN's Karl Penhaul. Drivers communicate via radio-telephones known in Spanish as "tren-tierras" or train-to-land. But drivers also use mobile phones if radio-telephones are not working or "when it's considered necessary," the spokeswoman said.
Steve Harrod, a railroad transportation expert at Ohio's University of Dayton, said he was stunned by the report that the driver may have been speaking on the phone shortly before the crash. In the United States, Harrod said, railroad drivers are not allowed to use cell phones to prevent dangerous distractions.
Shortly before the train crashed, according to reports, the Spanish train had passed from a computer-controlled area of the track to a zone that requires the driver to take control of braking and acceleration, Harrod said. "It's possible that the driver's phone conversation -- which apparently was part of his official capacity as a driver -- distracted him and he missed the transition from automatic to driver control," Harrod said. He may have been unaware he was in control of the train and realized, 'oh, no, we're headed for a curve.' If that's true, I really don't think it was his fault."
The Renfe spokeswoman told CNN that command and control posts have real-time systems to show each train's precise location at a given time. If this were the case, a controller who would have phoned the train driver might have known the train was approaching a curve.
According to an interview in state-owned Efe news service with the president of the state-owned Administrator of Railway Infrastructures, the train should have started slowing down about 4 kilometers (2.48 miles) before the curve. At 192 kph, the train would have been traveling about 3.2 kilometers a minute.
He hit the brakes seconds before the crash, bringing the speed down from 192 kph (119 mph), according to the court. He was still on the phone when the train flew off the tracks.
Of the 79 who died in the ensuing wreck, 63 were from Spain. Others were from the United States, Latin America and Europe.
The victims were remembered Monday in a memorial Mass at a Catholic cathedral in Santiago de Compostela.
"Our brothers lost their lives ... when they had so many plans," said Archbishop Julian Barrio." It is not easy to understand and accept this reality," he said, "but I say to you, let our pain not be wasted. Everything has meaning in our lives. We are not shouting in a vacuum."
CNN's Karl Penhaul, Thom Patterson, Marilia Brocchetto and Jason Hanna contributed to this report.