Sounds quite simular to the Japanese Hospital ship, S.S. Awa Maru, that was sunk off Formosa on April 1, 1945 by the
U.S. Submarine, USS Queenfish [SS-393]. The Awa Maru went down quickly, and there was only one survivor, a
Japanese steward. He was all the U.S. Needed to Courts Martial the skipper of the Queenfish for sinking a properly
marked hospital ship. Rumors aboud that she was carrying quite a bit of contraband...... rubber, gold, silver, ammo, etc.
More info here:
Awa Maru - Wikipedia, the free encyclopedia
Charles