Police spokesman Micky Rosenfeld says the boy was arrested on Monday. Questioned by police, he told them he had been smoking a water pipe last Thursday and threw some burning coals into an open area in the Carmel forest in northern Israel.
Rosenfeld says the boy told police he panicked, fled the scene and returned to school without telling anyone as the fire quickly spread through the forest.
Rosenfeld would not say how police found the boy, or whether he was connected to other suspects. Police have two other youths under house arrest.
Forty-two people died in the blaze.
