By Ben Klayman WARREN Mich. (Reuters) - General Motors Co on Thursday issued a report detailing how for 11 years it turned a blind eye to an ignition-switch problem linked to at least 13 deaths but largely pinned the blame on what the report described as incompetent lower-level employees, leaving top brass untouched. The report, which will be the subject of upcoming congressional hearings, describes shortcomings of GM engineers, including a failure to understand "how the car was built." Meanwhile, according to the 325-page report, the highest levels of the company were not made aware. Providing a rare peek into the operations of one of the world's biggest automotive companies, the internal investigation said GM had a long-running corporate culture in which nobody took responsibility for problems. The "GM nod" was how CEO Mary Barra described that culture, "when everyone nods in agreement to a proposed plan of action, but then leaves the room and does nothing," the document said.