BP...has engaged in a "cover up scheme" to hide its culpability for the deadly rig explosion that spawned last year's massive oil spill in the Gulf of Mexico, one of the oil giant's partners in the drilling project claims in a newly filed lawsuit. Halliburton['s]...suit...accuses BP of concealing critical information about the deepwater well that blew out on April 20, 2010...In response to the suit, which seeks unspecified monetary damages, BP spokesman Scott Dean accused Halliburton of trying to deflect blame and divert attention from its role in the disaster. Dean said "multiple independent investigations" have identified "serious problems" with the cementing of the well.