National Public Radio: In the 193-page internal report posted Wednesday on BP’s website, the British oil giant says the April disaster was caused by “a sequence of failures involving a number of different parties.” “It is evident that a series of complex events, rather than a single mistake or failure, led to the tragedy. Multiple parties, including BP, Halliburton and Transocean, were involved,” outgoing CEO Tony Hayward said in the report. The accident killed 11 workers aboard the Deepwater Horizon …