The corporations have turned on each other: Transocean, the company that operated the Deepwater Horizon Oil rig, has accused BP of withholding critical evidence that it says sheds light on the cause of the explosion that led to the worst offshore oil spill in American history. In a letter to BP’s attorney, Transocean says BP’s intransigence has hindered its investigation into the deaths of 11 rig workers. "This is troubling, both in light of BP's frequently stated public commitment to openness and a fair investigation, and because it appears that BP is withholding evidence in an attempt to prevent any entity other than BP from investigating the cause of the April 20 incident and the resulting spill," the letter said. Transocean accuses BP of rejecting at least seven requests for information and of ignoring requests for information since August 3. BP denies withholding information.