An internal probe conducted by British energy giant BP Plc (BP,BP.L) has found that no single factor caused the explosion on a Gulf of Mexico oil rig that led to the biggest environmental disaster in US history.
The company accepted partial blame for the April 20 explosion and fire that killed eleven of the 126 workers on the rig, but also pointed a finger at partners Transocean and Halliburton.
BP's investigation suggested a sequence of failures involving a number of different companies and work teams led to the Deepwater Horizon rig blowout and the resultant oil spill from the Macondo well.
The report blamed the accident on "a complex and interlinked series of mechanical failures, human judgments, engineering design, operational implementation and team interfaces."
"It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, Halliburton and Transocean, were involved," BP's outgoing chief executive Tony Hayward said in a statement.
Hayward said a faulty cement job and failure of the shoe track barrier at the bottom of the well let hydrocarbons from the reservoir into the production casing.
"The negative pressure test was accepted when it should not have been, there were failures in well control procedures and in the blow-out preventer; and the rig's fire and gas system did not prevent ignition," he added.
The investigation team has also proposed a total of 25 recommendations designed to prevent a recurrence of such an accident. These recommendations include strengthening assurance on blow-out preventers, well control, pressure-testing for well integrity, emergency systems, cement testing, rig audit and verification, and personnel competence.
The internal probe report was compiled by an over 50 member investigation team led by BP's head of Safety Operations Mark Bly, following a four-month investigation.
Earlier, BP capped the well in mid-July to choke the 107-day old BP oil spill for the first time since the BP-leased Deepwater Horizon rig explosion on April 20. It also completed cementing operations at the damaged Gulf of Mexico well as part of the static kill procedure.
Meanwhile, BP is expected to permanently plug the well very soon by starting to pump in heavy drilling mud and cement through a relief well, which is nearing completion, in a procedure known as "bottom kill." BP said it continues to work with the guidance and approval of the National Incident Commander and the leadership and direction of the federal government.
The broken well spewed an estimated 5 million barrels of oil worth around $400 million into the Gulf so far after the explosion, according to U.S. government scientists. The total volume of oil collected or flared by the containment systems so far is said to be about 826,800 barrels.
BP revealed last week that the oil spill has cost it a whopping US$8 billion until now, including cost of the spill response, containment, relief well drilling, static kill and cementing, grants to the Gulf states, claims paid and federal costs. As of August 23, there were 154,000 individual and business claims filed, against most of which $399 million have been disbursed.
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June 12, 2026 17:14 ET Major central bank action was the focus this week in economic news. The European Central Bank became the first major central bank to move in response to the rising inflationary pressures in the backdrop of the conflict in the Middle East. In North America, the U.S. inflation and trade data as well as Canada’s central bank decision gained attention. The Chinese trade data was the main news in Asia.