South Korea found a third suspected North Korean drone on a mountain on the east coast, officials said Sunday, in what could be the latest in a series of border incursions by North Korea's unmanned spy aircraft. South Korean soldiers found the crashed drone on a mountain in Samcheok, 290 kilometers east of Seoul, earlier in the day after three local residents informed the military that they had seen the unmanned aircraft on Oct. 4, defense ministry officials said.