Report : Interior Department , Transocean , regulators focused too heavily on personal injury issues . The disaster began on April 20 , 2010 , when an explosion aboard the Deepwater Horizon drilling rig killed 11 people and caused a three-month-long oil spill , sending nearly 5 million barrels of crude spewing into the Gulf . `` A number of past CSB investigations have found companies focusing on personal injury rates while virtually overlooking looming process safety issues -- like the effectiveness of barriers against hazardous releases , automatic shutoff system failures , activation of pressure relief devices , and loss of containment of liquids and gases , '' CSB Chairman Rafael Moure-Eraso said . Past investigations saw companies `` virtually overlooking looming process safety issues '' thousands people died and nearly 5 million barrels of oil spilled in the three-month Gulf of Mexico disaster . Report : BP needs to a better job of reporting major accident risks .
Report : Interior Department , Transocean , regulators focused too heavily on personal injury issues . Past investigations saw companies `` virtually overlooking looming process safety issues '' thousands people died and nearly 5 million barrels of oil spilled in the three-month Gulf of Mexico disaster . Report : BP needs to a better job of reporting major accident risks .