Researchers have discovered the remains of a Japanese mini-submarine they say was used to attack Pearl Harbor on Dec. 7 1941, the Los Angeles Times reports.

The discovery provides evidence that the submarine fired its torpedoes at Battleship Row and could therefore resolve a long-standing dispute among historians, the paper reports.

Five mini-submarines were intended to be used to launch a strike against Pearl Harbor, but four ended up not being used for various reasons, the paper reports. No one knew what happened with the fifth sub.