Japan’s SS Montevideo Maru was sunk in 1942 by a US submarine unaware that more than 1,000 prisoners of war were onboard.

The ship was sunk on July 1, 1942, en route from what is now Papua New Guinea to China’s Hainan, by a United States submarine whose crew did not realise the ship carried prisoners of war. The location of the wreck had remained a mystery for more than 80 years.

The vessel was found at a depth of more than 4 km (2.5 miles), the maritime archaeology group Silentworld Foundation, which organised the mission, said on Saturday.

The sinking of the Montevideo Maru was Australia’s worst maritime disaster, killing an estimated 979 Australian citizens including at least 850 soldiers. Civilians from 13 other countries were also on board, the foundation said, bringing the total number of prisoners killed to about 1,060.

“At long last, the resting place of the lost souls of the Montevideo Maru has been found,” Australia’s Prime Minister Anthony Albanese said in a tweet.

“Among the 1,060 prisoners on board were 850 Australian service members – their lives cut short,” he said.

“The extraordinary effort behind this discovery speaks for the enduring truth of Australia’s solemn national promise to always remember and honour those who served our country,” he added.

“We hope today’s news brings a measure of comfort to loved ones who have kept a long vigil.”

At long last, the resting place of the lost souls of the Montevideo Maru has been found.

Among the 1,060 prisoners on board were 850 Australian service members – their lives cut short.

We hope today’s news brings a measure of comfort to loved ones who have kept a long vigil. pic.twitter.com/husOu6peUL

— Anthony Albanese (@AlboMP) April 21, 2023

The long-awaited find comes ahead of April 25 commemorations for Anzac Day, a major day of remembrance in Australia and New Zealand for their troops killed in all military conflicts.

“This brings to an end one of the most tragic chapters in Australia’s maritime history,” Australia’s Defence Minister Richard Marles said in a video message.

“The absence of a location of the Montevideo Maru has represented unfinished business for the families of those who lost their lives until now,” Marles said.

Explorers began searching for the wreck on April 6 in the South China Sea northwest of the Philippines’s main island of Luzon and made a positive sighting just 12 days later, using high-tech equipment including an autonomous underwater vehicle with sonar.

“The discovery of the Montevideo Maru closes a terrible chapter in Australian military and maritime history,” said John Mullen, director of the Silentworld Foundation, which conducted the hunt with Dutch deep sea survey firm Fugro along with help from the Australian military.

“We’re looking at the gravesite of over 1,000 people,” he told Australia’s ABC News Breakfast.

“We lost nearly twice as many [Australians] as in the whole of the Vietnam War, so it’s extraordinarily significant for families and descendants,” he said.