HOUSTON -- An Associated Press investigation shows cutoff valves like the one that failed to stop the Gulf of Mexico oil disaster have repeatedly broken down at other wells in the years since federal regulators weakened testing requirements.
These steel monsters known as blowout preventers guard the mouth of wells and act as the last defense to choke off unintended releases.
While the precise causes of the April 20 explosion and spill remain unknown, investigators are focusing on the blowout preventer on the Deepwater Horizon rig operated by BP PLC as one likely contributor.
A detailed AP review of accident reports shows the devices have played a role in at least 14 accidents, mostly since 2005.
And government and industry reports have questioned the reliability of blowout preventers for more than a decade.