Mexico's top anti-drug prosecutor has resigned as part of a law enforcement shake-up amid a wave of continuing shootouts and executions. Employees of the Attorney General's Office who are not authorized to be cited by name say Noe Ramirez has resigned as Assistant Attorney General for Organized Crime. Ramirez has held that post since President Felipe Calderon took office one and a half years ago. The officials said Thursday that the resignation was part of a shake-up in anti-crime efforts requested by Calderon. Calderon's office said it could not confirm the resignation. Ramirez's apparent successor in the anti-drug office will be Marisela Morales, who previously headed up the agency's office on human trafficking.