On Thursday, a senior United Nations human rights official said he was investigating North Korea’s allegations that a dozen restaurant workers who arrived in the South from China last year were abducted against their will. The official said he spent part of a four-day visit to Seoul looking into the claims surrounding the biggest mass defection case involving North Koreans. North Korea says the 12 waitresses were abducted, and a manager who defected with them tricked them into making the journey. South Korea has claimed that they traveled voluntarily and were admitted on humanitarian grounds.