The panel also said neither that /*BP*/, its contractors nor federal regulators caught or corrected flawed decisions that contributed to the blowout.
The chairman of the 15-person panel pointed out that those failures would not be acceptable in companies that work with nuclear power or aviation.
Among the hazards highlighted in the report were 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 one month before the disaster, BP also lost drilling materials deep in the hole - a situation that hinted to the challenges of the well but was not used to address risks.
The panel also said it may not be possible to ever establish exactly what happened because much of the evidence was lost in the April explosion that killed eleven workers.
A final report is due June 2011.
The Associated Press contributed to this report.