A stuck pipe was to blame for last year's worst-ever oil spill as it impeded a system in place on the BP well to prevent pollution into the Gulf of Mexico, a study said.
A forensic test commissioned by the the US Department of Interior and Department of Homeland Security and released this week called for engineers to take a new look at design to prevent future accidents.
The study carried out by Det Norske Veritas, a Norwegian company that maintains construction standards, pointed to problems in the shear rams -- components meant to cut drill pipes as a last resort to avoid blowouts.
The flow from the well shoved the drill pipe into other parts of BP's Macondo well, preventing movement.
"The primary cause of failure was identified as the BSRs (blind shear rams) failing to fully close and seal due to a portion of drill pipe trapped between the blocks," the study concluded.
"It is recommended the industry examine and study the potential conditions that could arise in the event of the loss of well control and the effects those conditions would have on the state of any tubulars that might be present in the wellbore," it said.
The spill was set off when the Deepwater Horizon, a rig which BP leased to drill at the Macondo well, exploded on April 20, 2010, killing 11 workers.
More than 205 million gallons of oil gushed into the Gulf of Mexico, fouling US shorelines, closing rich shrimp and fishing grounds and scaring off tourists.
Explore further: Mexico sets greenhouse gas target for UN climate talks