Inside DuPont's deadly past

LA PORTE, TX (KTRK) -- Since 2010, the chemical safety board has investigated four incidents at DuPont facilities, including two cases at two different facilities where workers died.

Back in 2011, the U.S. Chemical Safety Board found "a series of preventable shortcomings" at a DuPont facility in Belle, WV, which contributed to a phosgene gas release in 2010 that killed a worker.

Also in 2010, an explosion during welding at a DuPont plant outside Buffalo, NY, killed one worker. Federal investigators blamed the company's failure to monitor flammable gas levels in a storage tank before the welding started for that deadly accident.