SEOUL, South Korea (AP) - South Korean authorities stepped up searches for 46 sailors still missing Saturday, hours after a naval ship sank near a disputed sea border with North Korea.Navy and coast guard vessels, as well as air force planes, were searching the waters near South Korea's Baeknyeong Island where the 1,200-ton Cheonan sank during a routine patrolling mission. The Joint Chiefs of Staff said rescuers had picked up 58 sailors but 46 still were missing. President Lee Myung-bak ordered officials to find the cause of the sinking quickly while keeping in mind all possibilities, presidential spokeswoman Kim Eun-hye...