During World War I, the Royal Australian Navy’s first submarine, AE1, was assigned to capture Germany's Pacific colonies. While the mission was a success, it turned tragic when AE1 and its crew disappeared—without a distress call—off the coast of Papua New Guinea on September 14, 1914. Now, following decades of mystery and multiple searches, AE1’s wreckage has finally been found, the Associated Press reports.

Furgro Equator, a Dutch survey vessel, located AE1 in mid-December as part of a search expedition funded partly by the Australian government. Submerged at nearly 1000 feet off the coast of Papua New Guinea's Duke of York Islands, the submarine is being treated as the grave site of its 35 crew members from Australia, England, and New Zealand.

Australian Government, © Commonwealth of Australia

According to a government press release, officials held a small memorial service for the deceased and are trying to contact their descendants. The Australian government will work together with the Papua New Guinean government to preserve the vessel’s wreckage and commemorate the tragedy.

As the first Allied submarine lost during World War I and the first ever lost by the Royal Australian Navy, AE1 holds a unique place in maritime history. It vanished just a day after the surrender of German New Guinea, but investigators ruled out enemy combat as an explanation for its disappearance; the only German ship nearby was a small survey boat.

Australian Government, © Commonwealth of Australia

Australian Government, © Commonwealth of Australia

Experts still don’t know what caused the vessel to sink. But because searchers at the time of its disappearance never found an oil slick, debris field, or bodies, experts assumed that the sub had struck a reef and sunk while remaining intact. While this theory hasn't been verified, the wreckage should provide more clues.

[h/t Associated Press]