The account is in Memoirs of a Forward Artillery Observer 1944-1945, by James Russel Major. I find it quite plausible due to pressure alone. I suppose you'd have to have hatches open. This is from a study called: Pathophysiology of Blast Pressure Waves. It goes on to detail gastrointestinal, brain and even heart injuries and deaths caused by pressure, but from my reading it seems that cases with no external signs (bleeding from the ears, etc), the most common cause of death would be pulmonary.