Secretary of State Hillary Rodham Clinton calls the evidence overwhelming" that the Cheonan, a South Korean warship that sank in March, was hit by a North Korean torpedo. Vice President Joe Biden has cited the South Korean-led panel investigating the sinking as a model of transparency. But challenges to the official version of events are coming from an unlikely place: within South Korea. Armed with dossiers of their own scientific studies and bolstered by conspiracy theories, critics dispute the findings announced May 20 by South Korean President Lee Myung-bak, which pointed a finger at Pyongyang. They also question why Lee made the announcement nearly two months after the ship's sinking, on the very day campaigning opened for fiercely contested local elections. Many accuse the conservative leader of using the deaths of 46 sailors to stir up anti-Communist sentiment and sway the vote. The critics, mostly but not all from the opposition, say it is unlikely that the impoverished North Korean regime could have pulled off a perfectly executed hit against a superior military power, sneaking a submarine into the area and slipping away without detection. They also wonder whether the evidence of a torpedo attack was misinterpreted, or even fabricated. "I couldn't find the slightest sign of an explosion," said Shin Sang-chul, a former shipbuilding executive-turned-investigative journalist. "The sailors drowned to death. Their bodies were clean. We didn't even find dead fish in the sea."