Spanish investigators are questioning a driver of the train that derailed in northern Spain, killing 80 people in what is described as the nation's worst rail disaster in 40 years.
Reports say the train may have been travelling more than twice the 80 kilometer per hour speed limit at the time of the crash outside Santiago de Compostela. More than 140 people were injured.
Spanish authorities have opened two investigations into the derailment - one by judicial authorities and another by the public works department. Officials say one of the train drivers, who is hospitalized with injuries, is being questioned by police.
On Thursday, Spanish Prime Minister Mariano Rajoy, who was born in Santiago de Compostela, visited the crash site and the hospital where many of the injured are being treated.
"For a native from Santiago, like me, believe me this is the saddest saint's day of my entire life. In my name, in the name of the government of Spain, and in the name of all those Spaniards who might feel represented by what I am going to say, I want to transfer my condolences to all families and friends of people who have died, who unfortunately, there are too many of."
He declared three days of mourning to honor the victims of the crash.
The state-owned railway company Renfe says the train was heading to the coastal town of Ferrol from Madrid when it crashed Wednesday night.
Recovery teams used cranes Thursday to move the carriages from the scene of the derailment.
The crash occurred on the eve of the city's annual religious festival of St. James, an event attended by thousands of Christian pilgrims from around the the world.
U.S. President Barack Obama said in a statement that he was "shocked and saddened" by news of the crash. He offered "heartfelt gratitude" to the Spanish government and rescue personnel who located and treated the injured.
Several foreigners were among the injured -- including five Americans and at least one Briton -- and the dead included a U.S. citizen.
The derailment is Spain's deadliest train crash since 1972 when a train collided with a bus in southern Spain, killing 80 people.