Rescue workers have so far recovered 73 bodies from the accident site.
Galicia’s Supreme Court spokeswoman said that four more people died in hospital while undergoing treatment.
Government officials said they believed the crash was an accident.
However, they said that no statement would be made regarding the cause without a proper investigation.
"We are moving away from the hypothesis of sabotage or attack," one official said.
According to the BBC, images from the site showed bodies covered with blankets next to the tracks as emergency crews searched the wreckage.
Alberto Nunez Feijoo, the leader of the regional government described it as "a Dante-esque scene", in comments to Radio Cadena Ser.
Prime Minister Mariano Rajoy convened an emergency ministerial meeting late on Wednesday.
He is due to visit the scene of the accident today.
"I want to express my affection and solidarity with the victims of the terrible train accident in Santiago," said Rajoy.
More than 140 passengers were receiving treatment for a range of light to more serious injuries, a health official told reporters on Thursday morning.
