Halliburton Co. used flawed cement in BP Plc's doomed Gulf of Mexico well, which could have contributed to the blowout that sparked the worst offshore oil spill in U.S. history, a White House panel said on Thursday.
Halliburton's shares tumbled as much as 16 percent after the National Oil Spill Commission released a letter detailing the panel's findings, before recovering to close down nearly 8 percent at $31.68 per share on the New York Stock Exchange. BP's U.S.-listed shares closed up 1.3 percent at $40.60 per share.
While not absolving BP of responsibility, the report heaped criticism on Halliburton's cement job, raising investor concerns it could be forced to bear some of the clean-up costs. BP has taken a $32.2 billion earnings charge to cover the cleanup.
The cost to insure Halliburton's debt jumped on the news.
Halliburton had run a series of tests that showed the material was unstable in the weeks before the April 20 explosion on the Deepwater Horizon rig, which killed 11 workers and spurred a temporary ban on deepwater U.S. drilling.
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