NEW YORK (CNNMoney) -- The oil spill at BP's Deepwater Horizon rig in the Gulf of Mexico was caused by a piece of drill pipe trapped in the platform's blowout preventer, which kept the device from working properly to stop the flow of oil into the Gulf, according to a report issued Wednesday.
The report, which was commissioned by U.S. agencies including the Interior Department and Department of Homeland Security, is the first forensic investigation into what went wrong aboard the BP-leased offshore drilling rig in April.
The Norwegian firm Det Norske Veritas performed the investigation of the blowout preventer on behalf of the agencies.
The drill pipe, part of the rig's blowout preventer, buckled under intense pressure and became trapped in a way that prohibited the close-off mechanism from fully stopping the flow of oil into the Gulf.
Specifically, the report says the blind shear rams -- designed to cut through the well pipe and seal it -- failed to close completely and seal the well because the drill pipe had become trapped between the ram blocks.
In order to conduct the study, the blowout preventer was raised from the ocean floor in September and moved to a NASA facility in New Orleans.
Included in the report are a list of recommendations for items in need of further study, such as the testing of back-up systems and the effectiveness of remotely operated vehicle interventions.
In January, the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling released a report that spread blame for the Gulf of Mexico oil spill among BP (BP) and Transocean (RIG), the drilling rig's owner, as well as Halliburton (HAL, Fortune 500), which installed the rig's cement casing.
"The findings confirm that the blowout preventer was in proper operating condition and functioned as designed," a spokesperson from Transocean told CNNMoney in an emailed statement. "High-pressure flow from the well created conditions that exceeded the scope of blowout preventer's design parameters."
The commission said that problems with deepwater drilling are "systemic" and that only "significant reform" will prevent another disaster.
The Interior Department said a much broader report that relies on additional sources of data -- including eyewitness accounts and photographs -- will be released this summer.
The April 20 explosion on the Deepwater Horizon rig killed 11 men and injured 17, launching the worst oil spill in U.S. history. The well was capped three months later, but not before millions of barrels of oil spilled into the Gulf.
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