A presidential panel report on the likely causes of the April BP (NYSE: BP) Gulf of Mexico tragedy is hot off the press. The blowout on Transocean's (NYSE: RIG) Deepwater Horizon rig caused an explosion, fire, 11 deaths, the sinking of the rig, and vast environmental damage. While the report appears to provide some legal and financial cover for BP, it also arrives at its conclusions without factoring in a key part of the puzzle.

According to the report, a synopsis of a lengthier version due out next week, BP and two of its major contractors, Transocean and Halliburton (NYSE: HAL) -- which was responsible for cementing part of the well -- were all at fault to one degree or another in the tragedy. Furthermore, rather than representing errors specific to this particular accident, the report suggests that the mistakes made were essentially systemic, occurring as a result of common industry practices.

While the commission chastens BP for excessive changes in the well design, it also finds fault with Halliburton's failure to properly test the cement used in the well, and takes Transocean to task for failing to educate its crew on the lessons that might have been learned from a similar incident aboard another of its rigs in the North Sea.

But as your friendly analyst -- and one with some time spent in the offshore drilling industry -- it seems to me that, while the conclusions reached by the panel might be basically sound, they're nevertheless are compromised by a missing piece of evidence.

The report doesn't mention that the blowout preventer -- which was manufactured by Cameron International (NYSE: CAM) and designed to thwart exactly the sort of catastrophe that occurred in the Gulf -- failed to operate on the Deepwater Horizon. There's no indication why it malfunctioned, and the huge piece of equipment is undergoing forensic testing at NASA's New Orleans facility. But as far as I'm concerned, until evidence about the blowout preventer is plugged into an examination, the report's conclusions risk becoming less accurate.

Beyond that, ExxonMobil (NYSE: XOM) CEO Rex Tillerson rejected the report's contention that standard industry procedures led to the blowout of BP's well. As he said, "The commission did not investigate the entire industry. It seems to ignore years ... of good performance, so I do not agree with that conclusion."

In the meantime, there are other pending investigations, including one by the Justice Department and another being conducted jointly by the Coast Guard and the Bureau of Energy Management. As such, it appears the most that can be concluded by the initial commission report is that it likely spreads the blame for the accident, reducing the possibility that BP will be found guilty of gross negligence.

That's likely a good thing for any Fools considering dipping into some BP shares.

 The Fool owns shares of ExxonMobil. Try any of our Foolish newsletter services free for 30 days.

Fool contributor David Lee Smith doesn't own shares in any of the companies named above. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.