CARBONDALE, Ill., April 26 A bomb scare at Southern Illinois University in Carbondale, Ill., was triggered by what turned out to be a prop for a class project.The campus was evacuated for nearly an hour while police investigated a mysterious package that was dropped off, which turned out to be a 60-pound bag of Sakrete concrete mix, Carbondale's The Southern reported Thursday.Police learned that Southern Illinois University senior Mark McArthur dropped the package off to use for a later group presentation on international marketing in the same classroom, the newspaper said.Henry McGee, who was in McArthur's group, told The Southern that a presentation was planned on a multivitamin rice additive that could be marketed to China."He brought in a bag of sand to show a comparable product," McGee said. "He dropped it off before the presentation and I think it was misinterpreted." Copyright 2007 by UPI