BP accused of stonewalling by drilling partner

NEW YORK (CNNMoney.com) -- Transocean, the company that owned the ill-fated drilling rig in the Gulf of Mexico, lashed out at well owner BP Thursday, accusing the oil giant of stonewalling the investigation into the Gulf disaster.

The drilling company accused BP (BP) of failing to provide documents critical for Transocean to determine exactly what caused its drilling rig, the Deepwater Horizon, to explode and subsequently sink last April.

"BP has continued to demonstrate its unwillingness, if not outright refusal, to deliver even the most basic information to Transocean," said the letter, sent to BP and members of Congress. "It appears BP is withholding evidence in an attempt to prevent any entity other than BP from investigating the cause of the incident."

Transocean (RIG) said it has asked for the information, which includes logs and test results in the days leading up to the explosion, at least seven times.

In the letter, Transocean's lawyers noted that BP agreed to provide some information earlier this summer, but made Transocean sign a confidentiality agreement before doing so.

A BP spokesman said the company is "disappointed" with Transocean's letter and called the allegations "misguided."

"We have been at the forefront of cooperating with various investigations, BP spokesman John Curry said in a statement to CNN. "Our commitment to cooperate with these investigations has been and remains unequivocal and steadfast."

Transocean said it wants the information to conduct its own internal investigation into the incident, which claimed 11 lives and caused the worst oil spill in U.S. history. It also said the information could be useful in making drilling practices safer industry-wide.

But much is at stake in the investigation. Although BP is responsible for all the costs to clean up the oil and has committed $20 billion to offset economic damages to the region, experts say lawsuits could drag on for years and involve all the companies involved in the doomed project.

If BP is found to have acted negligently in the days and weeks leading up to the explosion, that could greatly reduce the liabilities for BP's partners in the well and make things costlier for BP.

Evidence presented in Congressional hearings suggests BP managers aboard the drill rig pushed ahead with faster and cheaper methods for drilling the well, sometimes against the advice of its contractors.

BP contracts included Transocean and Halliburton (HAL, Fortune 500). Oil firms Anadarko (APC, Fortune 500) and Japan's Mitsui are also part owners in the well, and could see their liabilities decreased if BP is found negligent.

There are several ongoing investigations into the incident, and they are not expected to be completed for months.