By Ken Ward Jr. Two explosions that killed a total of three workers at a Barbour County industrial site occurred while the workers were draining cleaning chemicals from tanks used to store the materials that give natural gas its distinctive odor, the U.S. Chemical Safety Board said in a brief update issued Friday. CSB investigators said that both explosions at Midland Resource Recovery likely occurred when "unintended chemical reactions" caused "highly reactive or unstable chemicals" to form in the two tanks, but did not hint at what those reactions might have involved. "The CSB is continuing to investigate the primary causal factors of both incidents," the CSB said in a two-page document it called a "Factual Investigative Update." The board added, "Among the areas of interest, the investigation will examine the potential chemical reactions that could have led to the incident, potential learnings for other industries using reactive chemicals, and the process safety management systems in place at the MRR facility." The first explosion at the Midland Resource Recovery facility near Philippi occurred on May 24.