Patrolling American submarine sunk Japanese merchant ships according to the U.S. Joint Intelligence Committee. Daily summary dated 29 April 1942

An item reported that a patrolling American submarine sunk a medium size enemy tanker and a smal cargo ship in the Fra East. The British Admiralty estimated that the Japanese lost 250,000 tons of shipping since th war broke out.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 140 dated 29 April 1942.