The government of Aruba this week ordered its 4,000 public employees to participate in a systematic search for an 18-year-old American tourist who disappeared on May 30. This is a national effort, said police commander Trudy Hassell. Natalee Holloway, a straight-A student, was visiting the Dutch Caribbean island with 100 classmates celebrating their graduation from an Alabama high school. The night before her scheduled flight home, Holloway went to a concert on the beach, then to a restaurant, and was last seen heading back to her hotel. Two recently fired security guards from a nearby hotel were arrested for questioning.