BY BILLIE STANTON ANLEU billie.stantonanleu@gazette.com -Seven rail cars that derailed downtown Sunday night were carrying inert, harmless ammonium sulfate - not the potentially explosive ammonium nitrate that officials initially identified.Burlington Northern Santa Fe Railway doesn't normally identify freight it carries for customers, RNSF spokesman Joe Sloan said Monday.But it did in this case because the idea that ammonium nitrate had spilled had caused such concern.The powder that spilled near the Martin Drake Power Plant, Fountain Creek and a residential neighborhood prompted concern among many city officials."We need to shine a spotlight on this issue.