A federal panel says a company knew of the explosive danger of dust throughout its Tennessee plant but didn’t do enough to prevent three separate blasts that killed five people last year. The U.S. Chemical Safety Board released a final report last week on the three accidents at the Hoeganaes Corp. plant in Gallatin, near Nashville. The report found that the dust was first noted by an insurance audit in 2008, which prompted safety testing by the plant. Company officials learned that the dust was combustible, but the federal panel found it didn’t properly follow through on its plans to prevent an accident.