This week, Congress is holding hearings to find out the cause of the disastrous oil spill in the Gulf of Mexico, which BP's CEO, Tony Hayward, has called an "unprecedented accident."

Aside from bringing to mind another recent, supposedly unforeseeable crisis, these claims of obliviousness to the risks of offshore drilling seem to be in stark contrast with numerous studies and statistics about the failures of safety equipment.

The BP oil spill in the Gulf was caused, by all accounts, when a device called a blowout preventer failed. The blowout preventer is the main line of defense against a spill, and to hear BP's spokesman Steve Rinehart explain it, the failure of this device "seemed inconceivable."

"I don't think anybody foresaw the circumstance that we're faced with now," he told The Associated Press.

Another spokesman echoed that sentiment.

"The sort of occurrence that we've seen on the Deepwater Horizon is clearly unprecedented," BP spokesman David Nicholas told the Associated Press on Friday. A blowout at that depth is "something that we have not experienced before."

The message stayed consistent even at the company's highest ranks.

BP's CEO told NPR that the blowout preventer is "the ultimate safety system on any rig," and there is "no precedent for them failing."

But statistics and documents from both regulators and industry suggest otherwise:

• Accident reports from the Minerals Management Service -- the agency regulating offshore drilling -- shows that blowout preventers "have failed or otherwise played a role in at least 14 accidents, mostly since 2005," according to the AP.
• As we've noted, in 2004, MMS questioned whether an integral part of the blowout preventer -- a piece of equipment known as shear rams -- would work in deepwater conditions like the conditions in which BP was operating.
• McClatchy reported last week that in 2003, a report co-authored by a Transocean executive warned of "poor reliability" of the blowout preventers. "Because of the pressure on getting the equipment back to work, root cause analysis of the failures is generally not performed," reads one line of the report. Transocean, the largest offshore drilling contractor in the world, owns the Deepwater Horizon rig that exploded and sank, causing the well to rupture. BP operated the rig.
• According to MMS statistics, 39 blowouts occurred between 1992 and 2006 -- all but one were in the Gulf of Mexico. From 2007 to 2009, MMS statistics show 19 more blowouts occurred, as Think Progress pointed out. (Think Progress has received funding from the Sandler Foundation, the same foundation that is currently our major funder.)

Despite these warning signs, in its exploration plan submitted to regulators, BP described the "unlikely event of an oil spill" as having "little risk of contact or impact to the coastline and associated environmental resources."

MMS officials, despite their concerns about equipment failure, never issued stricter safety requirements. In 1998, with industry support, the agency actually reduced the frequency of inspections of blowout preventers from once a week to once every two weeks.

MMS' Deputy Director Walter Cruickshank told AP that decision may be revisited. He said the agency felt blowout preventers "were performing the job they were supposed to perform," but that the incident in the Gulf "is going to make us re-examine that assumption."

We've put out several calls to BP. We'll update if they comment.