An explosion ripped through a school in southeastern Afghanistan, killing nine children and one adult, the U.S. military said Sunday. An Afghan official said the blast on Saturday evening in Paktia province was caused by a bomb, though the military said it was still unclear. "There was an explosion, that's all we know," American spokeswoman Master Sgt. Ann Bennett said. "Killed were four children, five teenagers and one adult." An eight-year-old boy injured in the blast was taken to an American military base for treatment, Bennett said. Paktia Gov. Asadullah Wafa said eight children aged 7-15 were killed and 15 other people injured, three of them critically. It was not clear if two had subsequently died of their wounds. The military initially reported that about 30 children and two adults were wounded. Bennett said the toll was revised after reports from U.S. medical teams sent to help.