Most of the victims appeared to be foreign nationals who ignored instructions to shelter in place and decided to try to flee in their cars, said Antonio Sanz, head of emergencies in the Andalusia region.
The flames had spread extremely rapidly in a wooded area around the town of Los Gallardos in Almeria province, a popular holiday destination.
Four people, who appeared to be British because the steering wheel of their car was on the right-hand side, died in one vehicle, he said.
Seven others were found dead after apparently abandoning their cars and attempting to escape on foot along a route that was not part of the evacuation plan.
"The consequences have been terrible. Everything seems to indicate that, in the case of the dead, the majority - or all of them - are foreign nationals," Sanz said on Friday.
The circumstances resemble those in neighbouring Portugal in June 2017, when a huge wildfire during a heatwave killed more than 60 people and injured dozens more, with half of the victims burned to death in their cars as they tried to flee.
A series of early summer heatwaves has triggered an early start to wildfire season in Spain. So far this year, about 57,000 hectares have burned, about half the annual average for the past two decades and making up 40 per cent of all the area burned in the European Union, according to the European Forest Fire Information System.
In 2025, a record heatwave in August provoked the worst wildfire season in three decades, charring 330,000 ha, an area twice the size of London.
"We usually don't see these fires until August. They're starting earlier now because the vegetation dries out sooner," Roman Garcia, a forest firefighter from Salamanca, said on state broadcaster TVE.
As authorities sought to identify the dead and track down the missing, anxious relatives from around the world posted messages on social media and local forums.
One woman said her daughter, who was driving a red Ford Fiesta and had her dog with her, was missing.
Another person from the United States said her brother had been among a group of 10 people who tried to escape through a valley next to a stream.
She shared the co-ordinates and asked emergency services to look for him.
The fire was believed to have started when a power cable came loose and fell on a patch of dry scrubland on Thursday, Pedro Ridao, mayor of the nearby town of Antas, told TVE.
Prime Minister Pedro Sanchez offered his condolences to the families of the victims and said he felt "enormous sadness and devastation".
The death toll makes it Spain's deadliest wildfire since 2005, when 11 firefighters were killed in a blaze in the central province of Guadalajara that was sparked by a barbecue.
That disaster prompted major changes to Spain's wildfire prevention and emergency response systems.
