 -- After being lost at sea for over a century, Australia’s first Allied submarine, the HMAS AE-1, has finally been found in waters near the Duke of York islands in Papua New Guinea.

A maritime mystery that eluded expeditioners for 103 years, the discovery of the 800-ton AE-1 submarine concludes what the Australian government has called the country’s "oldest naval mystery."

The disappearance of the submarine marked the first loss for the Royal Australian Navy during World War I.

The submarine went missing on Sept. 14, 1914, off Rabaul, Papua New Guinea with 35 Australian and British crewmates on board.

Efforts to locate the submarine took place earlier this week in waters off the coast of Duke of York Island. Led by The Royal Australian Navy in conjunction with several other search groups, this mission was conducted on a survey vessel dubbed the "Fugro Equator." Equipped with advanced search technology, the Fugro Equator located an object of interest under 300 meters of water that would later be confirmed as the AE-1.

Initial images captured during the expedition showed the vessel to be remarkably well preserved and in one piece. In a statement reported by BBC News, Australian Defense Minister Marise Payne said, “This is one of the most significant discoveries in Australia’s naval maritime history.”

The loss of the submarine was “a significant tragedy felt by our nation and our allies,” he added.

Following HMAS AE-1’s discovery, a small commemorative service was held by members aboard the survey vessel to remember and honor the officers and sailors who lost their lives 103 years ago.

“I truly believe this will bring peace of mind to the family and descendants ... perhaps, in time, we may discover what caused the submarine to sink,” Payne said.

According to the BBC, there are currently no plans to return the AE-1 to Australia. The Australian government is reportedly working with the Papua New Guinea government to potentially make arrangements to preserve the site and create a lasting commemoration in recognition of the crew.

Research and information gained from this monumental expedition will be held by the Australian National Maritime Museum.