03/18/2010 05:12 am ET | Updated May 25, 2011

Japanese Midget Sub Discovered: Pearl Harbor Mystery Solved, Says Team

Researchers believe that they have found a fifth "midget submarine" sent by the Japanese Empire to participate in the attack on Pearl Harbor in 1941. What's more, is that they believe the vessel may have fired torpedoes at the USS Oklahoma--an attack that would have caused lethal damage.

For almost 70 years, the 6-foot wide, 80-foot long vessel was unaccounted for (four others sent by Japan never made it to their intended target), but now researchers believe that it has been hiding in plain sight. Wired's Danger Room blog wrote about the find:

During a routine test dive, marine researchers spotted some unusual steel debris on the ocean floor near Pearl Harbor. The wreckage, investigators from the PBS series NOVA concluded, was likely the remains of a Japanese mini-sub scuttled by its crew after the attack...The remains of the sub were intermingled with wrecks of several U.S. amphibious assault vehicles, destroyed in a 1944 ammunition fire and later dumped in the ocean.

The find is detailed in by PBS's NOVA in a program set to air January 5. It follows recent discoveries of 2 larger Japanese submarines in November. The New York Times:

Researchers on Thursday announced the discovery of two World War II Japanese submarines, including one meant to carry aircraft for attacks on American cities and the Panama Canal, in deep water off Hawaii, where they were sunk 63 years ago.

The submarines, among five that were captured by American forces at the end of the war and taken to Pearl Harbor for study, were found off Oahu at a depth of about 2,600 feet

2,402 Americans died in the Dec. 7, 1941 attack.