An exhaustive internal investigation of General Motors Co.’s ignition-switch recall shortcomings found fault with the company’s legal team, but “confirmed” that its top lawyer did not learn about the safety issues until after the recall.

The investigation, led by former U.S. Attorney Anton Valukas, chairman of Jenner & Block, found GM’s handling of the recall was “riddled with failures which led to tragic results for many,” the company’s chief executive office said in a statement released with the report on June 5.