The 2010 BP oil spill in the Gulf of Mexico was primarily caused by a failure of a safety system that resulted in the explosion and destruction of the Deepwater Horizon oil rig. The incident is considered to be the worst oil leak in the history of the United States as of 2015.
The oil rig blew up due to a failure of the cement at the bottom of the well bore, which was intended to seal the natural gas and oil. As a result of the breakdown, the gas leaked out of the drilling pipe and caused a huge blowout that sank the rig and killed 11 people. The oil spill that ensued was finally brought under control after 87 days.