After the RAF investigative board completed its report on the Halifax crash on 1 July 1942, it was distributed to a restricted list of approved recipients, but not publicly divulged. In the interests of wartime secrecy, the announcement of Blumlein's death was not made for another three years. The investigative board, headed by AIB Chief Inspector Vernon Brown – who later also investigated the post-war "Star Tiger" and "Star Ariel" disappearances – and assisted by Rolls-Royce, who had made the Halifax's Merlin engines, found that the crash was caused by engine fire, attributed to the unscrewing of a tappet nut on the starboard outer engine, which had been improperly tightened by an RAF engine fitter while inspecting the engine some three hours prior to the crash.