The death toll from the train derailment outside the northwestern Spanish city of Santiago de Compostela has risen to 78, with more than 130 others injured, officials said Thursday.

Twenty of the people injured in the accident are listed in very serious condition.

Emergency services personnel have concluded the search for victims of Wednesday night's accident in the northwestern region of Galicia, judicial officials told Efe.

The process of identifying the victims is proceeding slowly because so many of the bodies are extremely disfigured, the officials said.

Three of the critically injured were not identified until Thursday, when relatives went to the hospital, health officials said.

The identification process "requires (following) a protocol and has its rules" since "you do not want to make mistakes in this area because they would be extremely serious errors," the national government's representative in Galicia, Samuel Juarez, said.

The accident was "apparently caused by a derailment and it is possible that speed may have had something to do with it," Juarez said, adding that people should hold off on reaching a conclusion until the investigation was completed.

The high-speed passenger train went off the tracks along the Madrid-Ferrol route.

Prime Minister Mariano Rajoy on Thursday announced that Spain would observe three days of mourning for the accident victims. EFE