Indiana State Fair officials have hired engineering firm Thorton Tomasetti to investigate the fatal stage collapse Saturday seconds before the country duo Sugarland stepped on that stage. The firm investigated the I-35 bridge collapse in Minnesota and worked for New York City to investigate what caused the World Trade Center towers to fall on 9-11. Indiana State Fair Commission chairman Andre Lacy says he’s aware many people want answers, but is asking people to understand their investigation will take some time. Lacy says the probe is in addition to the investigations by Indiana State Police and the Indiana Occupational Safety and Health Administration. Five people were killed when the stage was pushed over, apparently by a sudden and very strong wind gust.