BP released the findings of its internal investigation into the Deepwater Horizon explosion and oil leak in the Gulf of Mexico. The company said no single factor caused the Macondo well tragedy. Rather, a sequence of failures involving a number of different parties led to the explosion and fire which killed 11 people and caused widespread pollution in the Gulf of Mexico earlier this year. • Even after explosion and fire had disabled its crew-operated controls, the rig’s blow-out preventer on the sea-bed should have activated automatically to seal the well. But it failed to operate, probably because critical components were not working.