Rescue teams have made a grim discovery indicating the vessel has sunk with its 53 crew members on board.
Indonesian officials have declared no hope of finding any survivors from a missing submarine after navy rescuers found debris from the vessel.
Search crews are now operating under the understanding the submarine has sunk, having located items including parts of a torpedo straightener, a grease bottle and prayer rugs.
According to ABC News, it is unlikely any of the 53 crew members will be found alive.
Authorities lost contact with Indonesian submarine KRI Nanggala 402 after it submerged early Wednesday during a torpedo drill.
It was thought the crew would only have enough oxygen to survive until early Saturday and that deadline has now passed.
The Indonesian navy chief of staff said a scan had detected the submarine at 850 metres, well beyond its survival limits of up to 500 metres.
The discovery comes after concerns the submarine could have been crushed by water pressure if it sank to depths reaching 700 metres.
Australian and US ships have joined warships, planes and hundreds of military personnel searching for the stricken submarine.
“There’s been no progress yet,” said Navy spokesman Julius Widjojono.
“We are still combing the area.”
Despite hopes for a miracle, an oil spill spotted where the submarine is thought to have submerged pointed to possible fuel-tank damage, fanning fears of a deadly disaster.
“The oil spill is a bad sign,” said retired French vice-admiral Jean-Louis Vichot.
“If it’s from the submarine, then it is probably the end.”
The vessel was scheduled to conduct the training exercises when it asked for permission to dive. It lost contact shortly afterwards.
Authorities have not offered possible explanations for the submarine’s sudden disappearance or commented on questions about whether the decades-old vessel was overloaded.
The military has said the submarine, delivered to Indonesia in 1981, was seaworthy.
Neighbouring Singapore and Malaysia, as well as the United States and Australia, were among nations helping in the hunt with nearly two dozen ships deployed to scour a search zone covering about 34 square kilometres.
Australia’s HMAS Ballarat arrived on Saturday with a US P-8 Poseidon aircraft also helping to look for the craft.
Singapore’s MV Swift Rescue — a submarine rescue vessel — was expected later Saturday.
Indonesia’s military said earlier it had picked up signs of an object with high magnetism at a depth of between 50 and 100 metres, fanning hopes of finding the submarine.
But the passing of Saturday’s oxygen deadline was likely to mean the Southeast Asian archipelago would be added to a list of countries struck by fatal submarine accidents.
Among the worst was the 2000 sinking of the Kursk, the pride of Russia’s Northern Fleet.
That submarine was on manoeuvres in the Barents Sea when it sank with the loss of all 118 aboard.
An inquiry found a torpedo had exploded, detonating all the others.
Most of its crew died instantly but some survived for several days before suffocating.
In 2003, 70 Chinese naval officers and crew were killed, apparently suffocated, in an accident on a Ming-class submarine during exercises in 2003.
Five years later, 20 people were killed by poisonous gas when a fire extinguishing system was accidentally activated on a Russian submarine being tested in the Sea of Japan.
And in 2018, authorities found the wreckage of an Argentine submarine that had gone missing a year earlier with 44 sailors aboard.
– with AFP