An internal investigation by oil giant BP has found that no single factor caused a rig blast that led to the worst oil spill in the US.

The company's report said a 'sequence of failures' involving a number of different parties led to the explosion and fire which killed 11 people in the Gulf of Mexico earlier this year.

The BP report said decisions made by 'multiple companies and work teams' contributed to the accident, which arose from 'a complex and interlinked series of mechanical failures, human judgments, engineering design, operational implementation and team interfaces'.

The report was based on a four-month probe by the company's head of safety and operations Mark Bly. BP said the report was conducted independently by specialists drawn from inside and outside the company.

The report found that the cement and shoe track barriers used at the bottom of the Macondo well failed to contain oil and gas within the reservoir, as they were designed to do. It added that the results of a pressure test on the well were incorrectly accepted by BP and rig operator Transocean. It said Transocean's rig crew also failed to recognise and act on the flow of oil and gas into the well for a 40-minute period.

The investigation team has proposed a total of 25 recommendations, all of which BP says it will accept.