Hopes of rescuing dozens aboard a missing Indonesian submarine faded Saturday as its oxygen reserves were believed to have run out, turning the focus to retrieving the stricken vessel from waters off Bali.

As hundreds of military personnel took part in a frantic hunt for the KRI Nanggala 402, authorities said the German-built craft was equipped with enough oxygen for only three days after losing power.

But that deadline passed early Saturday with still no sign of the missing vessel and its 53 crew.

The submarine, one of five in Indonesia’s fleet, disappeared early Wednesday during live torpedo training exercises off the Indonesian holiday island. The vessel was scheduled to conduct the training exercises when it asked for permission to dive. It lost contact shortly after.

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.

There were concerns that the submarine could have broken apart as it sunk to depths reaching 700 meters, well below what it was built to withstand.

Authorities have not offered possible explanations for the submarine’s sudden disappearance or commented on questions about whether the decades-old vessel was overloaded.

Neighbouring Singapore and Malaysia as well as the United States and Australia were among nations helping in the hunt with nearly two dozen warships deployed to scour a search zone covering about 10 square nautical miles (34 square kilometers).