Story highlights Halliburton was a contractor for BP at the ill-fated Deepwater Horizon oil drilling operation

BP and its contractors have been locked in legal battles since last year

An explosion aboard the Deepwater Horizon killed 11 and injured 16

The explosion led to more than 200 million gallons of oil being released into the Gulf of Mexico

BP is accusing Halliburton of having "intentionally destroyed evidence" related to the explosion aboard an oil rig in the Gulf of Mexico that led to the worst oil spill in U.S. history.

The accusation comes in court papers filed by BP Monday in federal court in New Orleans as part of a lawsuit aimed at having sanctions imposed on Halliburton Energy Services Inc., which was a contractor for BP on the Deepwater Horizon oil rig. An explosion on the rig on April 20, 2010, killed 11 people working on the rig and injured 16 others. The explosion led to more than 200 million gallons of oil being released into the Gulf.

BP alleges in its filing that Halliburton destroyed evidence on cement testing and violated court orders by not bringing forth "inexplicably missing" computer modeling results.

"Halliburton has steadfastly refused to provide these critical testing and modeling results in discovery. Halliburton's refusal has been unwavering, despite repeated BP discovery requests and a specific order from this Court," the documents state.

"BP has now learned the reason for Halliburton's intransigence -- Halliburton destroyed the results of physical slurry testing, and it has, at best, lost the computer modeling outputs that showed no channeling. More egregious still, Halliburton intentionally destroyed the evidence related to its nonprivileged cement testing, in part because it wanted to eliminate any risk that this evidence would be used against it at trial," the BP papers say.

When reached for comment Monday, Halliburton spokeswoman Beverly Stafford said the company was reviewing the details of the motion.

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"However, we believe that the conclusions that BP is asking the court to draw is without merit and we look forward to contesting their motion in court."

The BP documents state that two Halliburton employees testified under oath about destroying notes and samples related to analyzing the stability of a similar cement mixture that was used in the failed oil well.

"[D]id you take down any notes about the slurry?" Halliburton Global Advisor in Gulf Cementing Rickey Morgan was asked during a deposition detailed in the court motion.

"No, ma'am," Morgan responded.

"You didn't take any pictures?"

"No, ma'am."

"And then you said you dumped out the sample?"

"Yes, ma'am."

"And you mentioned that the reason that you didn't document the test and you threw out the sample was because you were worried about it being misinterpreted in the litigation?"

"Yes, that's part of the reason, yes, ma'am," Morgan testified, according to the BP papers.

BP is seeking to have a "third-party specialist" examine a Halliburton computer, saying "such an examination might well recover the missing modeling results, or shed light on the circumstances of their apparent disappearance."

BP and its two contractors -- Halliburton and Transocean, which owned the Deepwater Horizon rig where the explosion occurred -- have been locked in legal battles since last year.

In September, the final federal report on the spill said BP, Transocean and Halliburton all share responsibility for the deadly explosion and ensuing oil spill.

The three companies "violated a number of federal offshore safety regulations," according to the report, which was issued by the Bureau of Ocean Energy Management, Regulation and Enforcement.

The report concluded that a key cause of the explosion was a faulty cement drilling barrier at the well site.

"The precise reasons for the failure of the production casing cement job are not known," the report stated. But the disaster was "the result of poor risk management, last minute changes to plans, failure to observe and respond to critical indicators, inadequate well control response, and insufficient emergency bridge response training by companies and individuals responsible for drilling" at the site.

BP was "ultimately responsible" for operations at the site "in a way that ensured the safety and protection of personnel, equipment, natural resources, and the environment," the report concluded.

But Transocean, as owner of the rig, also was "responsible for conducting safe operations and for protecting personnel onboard."

Meanwhile, Halliburton -- as a BP contractor -- was "responsible for conducting the cement job, and ... had certain responsibilities for monitoring the well," the report said.

A spokesman for BP said in September that the company agreed with report's conclusion.

"The Deepwater Horizon accident was the result of multiple causes, involving multiple parties, including Transocean and Halliburton," Scott Dean said. "BP (has) acknowledged its role in the accident and has taken concrete steps to further enhance safety. ... We continue to encourage other parties to acknowledge their roles in the accident and make changes to help prevent similar accidents in the future."

But in response to the report, Halliburton continued to deny any responsibility for the tragedy.

The report "incorrectly attributes the operation decisions to Halliburton," said Zelma Branch, a Halliburton spokeswoman. "Every contributing cause where Halliburton is named, the operational responsibility lies solely with BP. Halliburton remains confident that all the work we performed with respect to the ... well was completed in accordance with BP's specifications for its well construction plan and instructions."

Besides the oil, hundreds of thousands of gallons of chemical dispersant went into the water. At the peak of the crisis, in June 2010, 37% of Gulf waters -- a total of 88,522 square miles -- were closed to fishing due to contamination.