A federal agency on Wednesday called the fatal July explosion at a Fremont industrial facility, “a terrible tragedy,” that it said was completely preventable. The U.S. Chemical Safety and Hazard Investigation Board said the July 29 explosion and fire at Horizon Biofuels, which resulted in the death of a worker and his two young daughters, was caused by a “completely avoidable hazard.” “This terrible tragedy should not have happened,” CSB Chairperson Steve Owens said in a news release. “Preliminary evidence points to a combustible wood dust explosion, a well-known – and completely avoidable – hazard in wood processing.” …“At the time of this update, the Horizon Biofuels facility remains unsafe and officials have advised that people maintain a safe distance from the facility due to the potential for the structurally compromised building to collapse, preventing the CSB from approaching the building so far,” the agency said in a preliminary report.