A key piece of equipment that could have helped prevent the Gulf of Mexico oil spill was not connected properly when the Deepwater Horizon rig exploded, a BP executive has testified.
Eleven people were killed during the explosion on 20 April and millions of barrels of oil spilled into the gulf, causing massive environmental damage.
Harry Thierens, executive vice-president for drilling and completions, gave testimony before a United States federal panel investigating the disaster.
Three BP officials have declined to testify, while others have been unable to provide clear answers that investigators are looking for, Radio New Zealand's correspondent reports.
It is not known, for example, who was in charge aboard the rig when it exploded; why the pipes on a device designed to prevent oil from spilling after a blowout was not corrected properly; or why warnings from a Haliburton employee that the cement job on the well might not function properly did not halt the operation outright, amid safety concerns.
The government hopes the results of the investigation will help clarify what new rules and regulations should be put in place for the industry to prevent similar spills in the future.