    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 .