Two young boys began playing with a hand grenade they found in a field in rural Colombia were killed when it exploded, police said Saturday. The two Nasa Indian children, ages 5 and 9, died immediately from the blast Friday night in the Andean mountains near the town of Toribio, 250 miles southwest of the capital, Bogota, said Col. Luis de Jesus Celi, police commander of Cauca state. The mayor of Toribio, Arquimedes Vitonas, told The Associated Press by telephone that the boys were cousins and that the flying shrapnel also injured three of their relatives. "These boys were just starting their life," said Alba Nuri Ipia, the mother of one of them, crying as she spoke to Caracol television. The hand grenade was most likely left by Colombia's main rebel group, the Revolutionary Armed Forces of Colombia, or FARC, Celi said.