On 20 April 2010, the offshore drilling rig Deepwater Horizon exploded and caught fire in US waters of the Gulf of Mexico.
11 workers were killed in the explosion and 17 injured. The rig was owned by Transocean on lease to BP, which was the main operator and developer of the site, with Anadarko Petroleum and MOEX Offshore (part of Mitsui Oil Exploration) as minority co-owners.
Work on the well had been performed just before the explosion by Halliburton.
The 'blowout preventer' was built by Cameron International.
On 22 April, the rig sank.
Oil leaked from the ruptured well head until 15 July when it was temporarily stopped; approximately 4.9 million barrels of oil had leaked into the Gulf.
On 19 September 2010, the US government declared the well 'effectively dead'.
Oil directly affected coastal areas in Louisiana, Mississippi, Alabama, Florida and Texas.
People dependent on fishing and tourism have been severely affected, along with those in other industries, including some farther from the Gulf Coast.
Concerns have also been raised in relation to health hazards for clean-up workers and coastal residents, including harms allegedly caused by chemicals used to disperse the oil (made by Nalco).