An executive from the company that was BP’s cement contractor on the Deepwater Horizon drilling rig testified Monday that he learned of some “irregularities” in tests that the contractor’s employees performed after the massive 2010 oil spill in the Gulf of Mexico.

Timothy Probert, a Halliburton president who served as the company’s chief safety officer at the time of the spill, didn’t specify the nature of those irregularities during his testimony at a trial designed to assign fault to the companies involved in the deadly disaster.

However, an attorney for rig owner Transocean Ltd. asked Probert if he was angry when he learned in 2012 that “evidence had been destroyed.”

“Yes,” Probert said. “Obviously, it doesn’t make you feel happy.”

A plaintiffs’ attorney who questioned Probert earlier Monday claimed Halliburton employees conducted “off-the-record” cement tests and didn’t write down some test results because they feared how they could affect litigation spawned by the nation’s worst offshore oil spill.

In a December 2011 court filing, BP accused Halliburton of intentionally destroying evidence from its cement testing. BP said Halliburton employee Rickey Morgan analyzed a cement slurry with the same composition as the foam slurry that was pumped at the Macondo well and verbally reported the results to a supervisor in 2010.

“He testified that the slurry ‘looked thin,’ which he explained implied lower-than-expected viscosity, a property that reflects how stable the slurry is when mixed and pumped into the well,” BP attorneys wrote. “Significantly and remarkably, Mr. Morgan admitted under oath that he ‘threw out’ the slurry samples he tested because he was ‘worried about’ those materials ‘being misinterpreted in the litigation.”’

Probert, who testified as the trial entered its third week, also testified under oath before Congress about the company’s role in the drilling project shortly after the April 20, 2010, blowout of BP’s Macondo well. Probert said Halliburton provided Congress with some “clarifications” about his testimony after the fact, but he said he didn’t do that personally and didn’t know what was clarified.

“I didn’t know about any of the alleged testing until some considerable time after my testimony,” said Probert, who now serves as Halliburton’s president of strategy and corporate development.

Halliburton attorney Donald Godwin frequently interrupted and objected to some of the questions that plaintiffs’ attorney Jeffrey Breit posed to Probert. Godwin complained that Breit had no basis for implying that Halliburton employees “threw out evidence.”

U.S. District Judge Carl Barbier, who is hearing the case without a jury, told Breit he was better off asking other witnesses about Halliburton’s handling of evidence because Probert doesn’t have firsthand knowledge of the tests.

“I don’t know who threw away what or if anyone threw away anything,” Barbier said. “My point is Mr. Breit has the wrong witness on the stand.”

Probert said he didn’t have anything to do with the Macondo drilling project before the well blowout triggered an explosion that killed 11 workers and spewed millions of gallons of oil into the Gulf.

A series of government investigations have concluded that the blowout resulted from a complex web of mistakes and spread out the blame among BP and its contractors. One of those mistakes was the failure of the cement job, which allowed oil and gas to flow from the well.

Barring a settlement, the trial is expected to last several months before Barbier could decide how much more money the companies owe for their roles in the catastrophe.