BP will today publish the findings of an investigation into the causes of the Gulf of Mexico oil disaster which led to the largest offshore spill in history.
It remains unclear how much responsibility BP will take itself for the spill, which followed an explosion on the Deepwater Horizon oil rig in April in which 11 people were killed.
But it has been reported that the internal probe, led by the oil giant's head of safety and operations, Mark Bly, is expected to assign blame to BP as well as other companies involved in the well's operations.
The findings are expected to lay out why engineers missed key signs that the well was unstable, such as worrying pressure tests, reports said.
However, BP has refused to give an indication of the contents of the report before it is published.
Other companies expected to bear some of the blame are Transocean, which owned and operated the Deepwater Horizon rig, and Halliburton, which was responsible for cementing the well to secure it.
Further probes are being conducted into the disaster, including a US Department criminal investigation and a joint inquiry by the US Coast Guard and the US Bureau of Ocean Energy Management.
The explosion on April 20 killed 11 workers and caused an estimated 4.9 million barrels of oil to gush into the Gulf.
At the peak of the crisis, 3.5 million feet of containment boom was used to rein in the spill, although this has now been reduced to 1.72 million.
BP has come under heavy fire in the US but the political pressure has eased since the oil firm set up a US$20bn (€15.7bn) fund to meet compensation payouts and costs.
The crisis cost former chief executive Tony Hayward his job after a series of PR blunders and he will make way in October for fellow board member Bob Dudley, who becomes BP's first overseas boss.
The longer-term fall-out such as fines, penalties and potential legal action is also set to add to the bill and spread the pain over a number of years.
BP hopes to sell around 10% of its production assets over the next 18 months, with the aim of raising $30bn (€23.5bn) to beef up its balance sheet to meet the crisis.
BP has already spent $8bn (€6.2bn) trying to contain the disaster, and has forecast that it will eventually cost the group more than $32bn (€25.1bn), after clean-up costs and compensation are taken into account.