Police said in a statement that the boy is thought to have started the fire by using a lighter in an area of abundant dry vegetation.
The fire was started close to a villa and in a forested area containing pine trees and some eucalyptus trees.
Detectives have since revealed that they have been unable to establish “any rational motivation or plausible explanation” for the boy’s actions.
PJ police added that only the swift action of locals, coupled with the subsequent intervention of fire-fighters stopped the fire from reaching major proportions.
Due to the age of the child, he will not be facing any criminal charges, but the law does foresee specific educational procedures which could be decreed by the Castelo Branco magistrate’s court.