A Parrita high school student picked the wrong place to explode fireworks Tuesday morning. He set them off in the park in the center of town.
Fuerza Pública officers heard the blasts and investigated.
The basic rule in Costa Rica is if it explodes, it is illegal.
Police found the 18-year-old with 60 unexploded large firecrackers, called bombetas in Spanish.
Police said the youth will get a court hearing and that they are on the trail of those selling illegal fireworks to youngsters.