WASHINGTON (AP) -- The company that owned the Deepwater Horizon oil rig that exploded in the Gulf of Mexico is accusing BP of withholding what it describes as critical evidence needed to investigate the cause of the worst offshore oil spill in U.S. history, according to a confidential internal document obtained by The Associated Press.
In a sternly worded letter to BP's attorneys, Transocean said the oil giant has in its sole possession information key to identifying the cause "of the tragic loss of eleven lives and the pollution in the Gulf of Mexico," and that the company's refusal to turn over the documents has hampered Transocean's investigation and hindered what it has been able to tell families of the deceased and state and federal investigators about the accident.
"This is troubling, both in light of BP's frequently stated public commitment to openness and a fair investigation, and because it appears that BP is withholding evidence in an attempt to prevent any entity other than BP from investigating the cause of the April 20 incident and the resulting spill," the letter said. Copies of the letter were also sent to government agencies and lawmakers investigating the spill's cause.
President Barack Obama sternly warned months ago that companies involved in the accident needed to work together and with the government on the investigation, saying: "I will not tolerate more finger-pointing or irresponsibility."
BP spokeswoman Elizabeth Ashford confirmed that company had reviewed the letter, but called its accusations misleading and misguided, particularly the charge that BP was withholding evidence.
"We have been at the forefront of cooperating with various investigations commissioned by the U. S. government and others into the causes of the Deepwater Horizon tragedy," Ashford said. "Our commitment to cooperate with these investigations has been and remains unequivocal and steadfast."
Transocean owned the rig that exploded. Eleven workers were killed and 206 million gallons (780 million liters) of oil was spilled. BP was operating the rig, and the British company also was the majority owner of the runaway well.
Retired Coast Guard Adm. Thad Allen, the government's point man on the Gulf oil spill, told the AP during a conference call with reporters Thursday that he was not aware of Transocean's letter and could not comment on it. Asked if BP has withheld any information vital to the government, Allen said, "None that I am aware of."
According to Transocean, BP has rebuffed at least seven of its requests for information. And while BP has turned over some documents, it has not provided Transocean with any information since June 21, and has not even acknowledged the company's requests since August 3, the letter said.
Transocean said that certain limited information it has been able to retrieve from BP came only after the company reluctantly signed a confidentiality agreement.
"Ultimately, and despite our reservations, we agreed to BP's condition of secrecy because there is no other source of key well data," the letter says.
The company is seeking 16 pieces of technical information from BP, including pressure tests, logs, and other data.
In another development, the U.S. government said Thursday the final plugging of BP's blown-out Gulf well will begin sometime in early September.
First, engineers plan to replace a massive failed piece of equipment on the sea floor, a potentially risky maneuver.
Allen said he is ordering BP to come up with a way to replace the crippled blowout preventer without causing further damage or releasing more oil into the environment.
The blowout preventer was supposed to avert the explosion that sank the Deepwater Horizon, but it did not.
Replacing the blowout preventer should alleviate some of the pressure that could build up when a relief well BP is drilling intersects the blown-out well. BP will then use the relief well to plug up the blown-out well with mud and cement from the bottom, a procedure known as a bottom kill.
If everything goes as planned, the final plugging will begin after Sept. 6.
Allen said the decision on how to proceed was made overnight, just hours after he told reporters he wasn't giving a timeline.
He did not say why things came together so quickly. As to why it will take nearly three more weeks to begin the bottom kill, Allen said there are several steps that must be taken first.
"If you add all those sequences up ... it logically takes you to a point sometime after Labor Day," Allen said.
A cap has kept oil from flowing for more than a month, but that's just a temporary solution. Mud and cement was later pumped in through the top of the well, significantly reducing the pressure inside it.
But the government believes the bottom kill procedure is necessary to declare the well dead once and for all.
"We are very, very close to the end," Allen said.
Weber reported from New Orleans.