HONOLULU, Hawaii -- Researchers from the University of Hawaii have found proof of a key element in the 1941 Japanese attack on Pearl Harbor -- a midget submarine reported sunk by a U.S. naval ship barely an hour before the massive airstrikes began.

The university's Hawaii Undersea Research Lab discovered the submarine Wednesday off the mouth of the Harbor after a decade of searching.

The submarine was last seen around dawn December 7, 1941, when the destroyer U.S.S. Ward spotted its conning tower following another U.S. ship into the Harbor.

The Ward fired its guns at the submarine, forcing it to submerge, then dropped depth charges and reported it sunk barely an hour before the first Japanese planes tore into the U.S. fleet anchored in the Harbor, launching the United States into World War II.

The Ward's report of the sinking -- which could have provided warning of the impending attack -- was misplaced until it was too late.

The missing submarine -- one of five used in the attack -- was located about "three to four miles off the channel entrance, straight out and dead east off the mouth of the Harbor, about a thousand feet down.

It's in good condition and sitting upright, AFP reported.

There quite a lot of other debris nearby, which made it difficult to find," said John Wiltshire, the lab's acting director. "Both torpedoes are still in the tubes at the bow of the submarine. There's a hole in the conning tower that goes straight through, obviously from a cannon round."

The submarine's two crewmembers -- missing and presumed dead since the attack -- are believed to be entombed inside.

Discovering the final resting place of the first ship sunk in the Pacific war had been something of a personal mission for more than a decade for deep-diving submarine Pilot Terry Kerby and the rest of the lab's research team.

Kerby found the discovery exciting but sobering.

"This is the first victim of the pacific war, and no one has seen it since the moment it slipped under the waves on December 7. You look at it and see the hole in the side exactly the way the destroyer crew described it, and you also realize this is a time capsule of the last moments of the crew's lives."

Last year, a highly publicized National Geographic Television expedition starring woods hole explorer Robert Ballard -- discoverer of the Titanic and other well-known undersea wrecks -- investigated the area and came up empty-handed.