The alarm was raised around 5 a.m. on Friday in Villafranca de Ebro, about 28 kilometers (18 miles) from the northeastern city. Two people remained in critical condition, officials said.
The cause of the fire was not yet known.
Local media said 82 people had been living in the nursing home, which focused on treating people with dementia and mental health issues.
Jorge Azcon, head of the regional government of Aragon, which includes Villafranca de Ebro, told reporters outside the nursing home that an investigation would be opened into the cause of the fire.
For now, the priority was to transfer the remaining uninjured residents to other facilities, he said, including one in the city of Huesca, about 90 kilometers (56 miles) away. Volga Ramirez, mayor of Villafranca de Ebro, told reporters that intense smoke from the blaze was likely responsible for the deaths. “It is due to smoke inhalation,” Ramirez said, “not because they were burned.” She said that the remaining residents of the center had been safely evacuated.
Zaragoza fire chief Eduardo Sanchez told reporters that firefighters had extinguished a blaze in one room of the center.
On X, formerly Twitter, Azcon announced that all government events in the Aragon region were cancelled for the day.
Spanish Prime Minister Pedro Sanchez on X wrote that he was “shocked at the tragedy” and expressed condolences to the victims.
The fire took place just weeks after devastating flash floods in the Spanish region of Valencia killed more than 200 people and destroyed thousands of homes. The floods were the worst natural disaster in Spain’s recent history.