Shares of oil giant BP (BP) are lower on Tuesday after it was reported that US prosecutors are trying to decide whether or not to pursue manslaughter charges against managers for decisions made prior to last year's Gulf of Mexico rig explosion that killed 11 workers and resulted in the biggest oil spill in US history. BP has in the past admitted to mistakes made prior to the accident but has denied it was "grossly negligent." The firm could be exposed to tens of billions of dollars in increased liabilities if a court were to decide the firm were.