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WASHINGTON (Reuters) - The failure of the underwater blowout preventer that led to the massive BP oil spill in the Gulf of Mexico was caused by a stuck section of drill pipe that blocked cutting devices from shearing and sealing the leaking well, the U.S. government said Wednesday.
The cutting devices, known as blind shear rams, could not sever the pipe, according to a report commissioned by the Interior Department and U.S. Coast Guard. As a result, oil from the BP's Macondo well flowed freely into the Gulf.
"The primary cause of failure was identified as the (blind shear rams) failing to close completely and seal the well due to a portion of drill pipe becoming trapped between the ram blocks," according to a review of the blowout preventer, which was conducted by the Norwegian company Det Norske Veritas.
The report is the first forensic examination of the BP blowout preventer after it was brought up from the sea floor.
It does not change the conclusions of the White House's oil spill commission, which found that missteps by the oil industry and government regulators set in motion the events that ultimately led to the biggest offshore oil spill in U.S. history.
The blowout preventer used with the BP well was manufactured by Cameron International. The company's stock was already down 2 percent before news of the government report, but it fell another 2 percent after the report came out before recovering.
The shear rams were unable to move the entire pipe section into its blades because the drill pipe deformed and buckled.
"Once buckling occurred the (blind shear rams) would not have been able to completely close and seal the well. The buckling most likely occurred on loss of well control," the report said.
The Interior Department and Coast Guard will hold public hearings in New Orleans during the first week of April to focus on the examination of the blowout preventer.
The results of the forensic review released on Wednesday recommended the oil industry study ways to make sure shear rams can completely cut pipes regardless of their position within the wellbore and seal a well.
Those industry findings should be incorporated in the design of future blowout preventers and modifications to existing ones, the report said.
BP said in a statement it agreed with the report's recommendation that additional testing be done to provide a comprehensive view on why the blowout preventer (BOP) failed.
"We support efforts by regulators and the industry to make BOPs more reliable and effective," the company said.
Transocean Ltd, which owned the blowout preventer, said the report showed the device was in proper operating condition, but high-pressure flow from the well created conditions "that exceeded the scope of BOP's design parameters."
Representative Edward Markey, a strong critic of the oil industry, said the report raises doubt that blowout preventers can be the last lines of defence against oil spills and he called for a full review of all blowout preventers in the U.S.
"A blowout preventer is like a car's airbag. It can't prevent the car accident, but it is supposed to deploy and prevent fatalities," said Markey.
"It isn't clear from this report that blowout preventers can actually prevent major blowouts once they've started. We cannot turn a blind eye to the fact that the blind shear rams did not seem to work," he added.
Reporting by Tom Doggett and Ayesha Rascoe; additional reporting by Braden Reddall; editing by Sofina Mirza-Reid and Lisa Shumaker