Six pieces of debris believed to be from the submarine, which was lost in the Bali Sea on Wednesday, were presented to journalists.
The latest update came as hopes faded for the 53 crew members who were expected to have run out of oxygen early on Saturday.
The debris believed to be from the missing submarine included a bottle of grease, part of a torpedo launcher, part of a metal tube, prayer mats and fuel, Yudo said. It was found floating at a location where the sea is 850 meters (930 yards) deep.
People who were on a previous mission on the KRI Nanggala-402 submarine confirmed that some of the debris belonged to the submarine, the navy chief of staff said. The bottle of grease matches what the crew would use to lubricate the submarine’s periscope.
Yudo said an explosion was not believed to have occurred on the submarine but that heavy pressure on the vessel may have a created a crack through which some items escaped.
The United States is deploying a P-8 Poseidon submarine hunting aircraft to assist in the search and rescue operation for the submarine.
The Indonesian navy said it was sending search helicopters and ships to the area where contact was lost with the 44-year-old submarine on Wednesday as it prepared to conduct a torpedo drill.
Australia has also deployed a sonar-equipped frigate with a helicopter to help the submarine hunt, while a deep submergence rescue vessel is on route from India, as concerns grow the submarine might have been crushed by water pressure.
“The possibility of it having fallen underneath its maximum diving depth thereby leading to the implosion of the submarine will have to be considered,” said Collin Koh, research fellow at the Institute of Defense and Strategic Studies.
If the submarine is still intact, Indonesian officials said Friday it would only have enough air to last until about dawn on Saturday if equipment was functioning properly.
“So far we haven’t found it… but with the equipment available we should be able to find the location,” Achmad Riad, a spokesman for the Indonesian military, told a news conference.
Koh said the assumption the submarine had 72 hours of oxygen was optimistic given the submarine’s limited ability to generate oxygen due to its conventional power generation.
“So there’s a possibility…oxygen might have already run out,” Koh said.
Indonesia’s navy said it was investigating whether the submarine lost power during a dive and could not carry out emergency procedures as it descended to a depth of 600 to 700 meters (1,968 to 2,296 feet), well beyond its survivable limits.
The diesel-electric powered submarine could withstand a depth of up to 500 meters (1,640 feet) but anything more could be fatal, navy spokesman Julius Widjojono said.
Experts like Koh say Indonesia will have to expand the area of search again if the magnetic anomaly is proven not to be the vessel and warn that if the submarine is lost at an”extreme depth,” it might be possible to retrieve.
The Bali Sea can reach depths of more than 1,500 meters (4,921 feet).
One of the people on board was the commander of the Indonesian submarine fleet, Harry Setiawan.