FREMONT, Neb. — The U.S. Chemical Safety and Hazard Investigation Board (CSB) has opened a formal investigation into the July 29 explosion and fire at the Horizon Biofuels facility in Fremont that killed three people, officials announced Thursday. The blast fatally injured 32-year-old Dylan Danielson and his two young daughters who were inside the plant at the time. “This horrific incident should never have happened,” CSB Chairperson Steve Owens said in a statement. “We want to prevent a terrible tragedy like this from occurring again.” …The independent federal agency, whose members are appointed by the president and confirmed by the Senate, does not issue citations or fines but makes safety recommendations to companies, industry groups, labor organizations and agencies such as OSHA and the Environmental Protection Agency.