BP's first official report on what caused the catastrophic oil spill in the Gulf of Mexico in April says several companies, and not just BP, were to blame.
Eleven workers died when an oil rig exploded, causing huge quantities of oil to leak into the sea, but BP says no single factor caused the spill - the worst ecological disaster in recent American history.
The report, by BP's head of safety, Mark Bly, says a sequence of failures involving a number of different parties led to the explosion.
It concludes that the accident arose from a complex and interlinked series of mechanical failures, human judgments, engineering design and operational implementation problems.
BP says dealing with the spill has cost $US11 billion and it has so far paid out about $US550 million in claims to people affected.
Well design was 'fatally flawed'
The BBC reports that Transocean, the rig owner, has responded to the report by accusing BP of having designed a fatally flawed well.
"In both its design and construction, BP made a series of cost-saving decisions that increased risk - in some cases, severely," the BBC quotes Transocean as saying, citing Associated Press.
A number of investigations into the disaster are under way.