More than seven weeks after BP's Deepwater Horizon oil rig caught fire and sank, causing the worst environmental disaster in US history, what exactly happened during its final hours remains murky. There is broad agreement that the platform exploded shortly after a series of safety checks -- but just how many tests were done and what they revealed is the subject of intense speculation and debate. Now a lawyer for some of the survivors says he has new evidence that casts doubt on BP's claims that a key safety check was successfully performed just hours before the explosion.
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