    Sentence 1: Government workers  trapped in a burning downtown office  tower frantically dialed 911 as they tried  to make their way through smoke-filled  staircases and hallways, officials said ,    Sentence 2: Some people trapped in a  burning high-rise building in Chicago 's  Loop business district frantically dialed  911 for help in escaping the smoke-filled  staircases and hallways, officials said .