Experts feared that the vessel has sunk too deep to withstand the pressure of water on the hull.
Indonesian search teams have located the wreckage of a military submarine on the ocean floor and officially confirmed that all of its 53 crew members are dead.
The submarine went missing off the coast of Bali on Wednesday, sparking an international search and rescue operation that included Australian, American, Malaysian, and Indonesian boats and planes.
The authorities revealed early on that the crew would run out of oxygen in the early hours of Saturday while the depth to which it was believed to have sunk would be enough to crush the hull.
But they had stopped short of confirming the deaths of the 53 crew members until Sunday, when the images of the wreckage and debris on the ocean floor were received.
“We received underwater pictures that are confirmed as the parts of the submarine, including its rear vertical rudder, anchors, outer pressure body, embossed dive rudder, and other ship parts," military chief Hadi Tjahjanto told reporters in Bali on Sunday.
"With this authentic evidence, we can declare that KRI Nanggala 402 has sunk and all the crew members are dead."
An oil slick had previously been discovered close to where the wreckage was found, promoting Navy Chief of Staff Adm. Yudo Margono to speculate on Saturday that the crew may have released fuel and fluids to reduce the vessel’s weight that so it could surface again.
But he added that the submarine had sunk to a depth of 600-700 meters (2,000-2,300 feet), far deeper than its collapse depth of 200 meters (655 feet), at which the water pressure would have been greater than the hull could withstand.
The cause of the disappearance is still uncertain. The navy has said an electrical failure could have left the submarine unable to execute emergency procedures to resurface.
The German-built diesel-powered KRI Nanggala 402 has been in service in Indonesia since 1981. It was carrying 49 crew members and three gunners as well as its commander, the Indonesian Defense Ministry said.
Indonesia, the world’s largest archipelago nation with more than 17,000 islands, has faced growing challenges to its maritime claims in recent years, including numerous incidents involving Chinese vessels near the Natuna Islands.