In a 28-page report released late Tuesday, an independent panel convened by the National Academy of Engineering said the companies failed to learn from "near misses" and neither BP, its contractors nor federal regulators caught or corrected flawed decisions that contributed to the blowout.
Donald Winter, a professor of engineering practice at the University of Michigan and chair of the 15-member study committee, said in a statement that plugging of the well to seal it off for future oil and gas production continued "despite several indications of potential hazard."
Those hazards included several tests that indicated the cement at the bottom of the hole would not be an effective barrier to an influx of oil and gas. More than a month before the disaster, BP lost drilling materials deep in the hole - a situation that hinted to the challenges of the well, but was not used to mitigate risks.
The panel's interim findings - the second from an independent entity - are still in progress, but they echo much of what has been discovered in prior investigations by BP, lawmakers and the president's oil spill commission. The panel is still reviewing technical data, and forensic testing on the blowout preventer, which failed to halt the gusher as designed, got under way Tuesday.
Still, the report said it may not be possible to ever establish exactly what happened because much of the evidence was lost when 11 workers died and the rig sunk in April.
Interior Secretary Ken Salazar asked in May for the investigation by the academy, saying he wanted "an independent, science-based understanding of what happened."
A final report is due in June 2011.