Hundreds of firefighters, supported by helicopters and fixed-wing aircraft, battled Saturday to contain one of Spain's deadliest wildfires in recent years, which has killed at least 12 people.

Authorities said lighter winds and higher humidity have improved firefighting conditions, but the blaze's massive scale continues to hamper containment efforts. Antonio Sanz, head of Andalusia's emergency services, said the fire has already scorched about 66 square kilometers (25 square miles) of forest and farmland, an area roughly the size of Manhattan.

Fire crews carried out controlled burns overnight along the fire's perimeter in an effort to slow its advance, Sanz said. The blaze erupted late Thursday in a semi-arid area near the Sierra de los Filabres mountains in Almeria province during an intense heat wave across Spain.

Authorities said most of the victims, believed to be foreign nationals, died after disregarding shelter-in-place orders. Seven people were killed after abandoning their vehicles and attempting to escape on foot.

Regional authorities said four of the victims are believed to have been British because the burned-out vehicle they were traveling in had the steering wheel on the right side, a feature typical of vehicles registered in the United Kingdom.