The KRI Nanggala 402 went missing after its last reported dive Wednesday while participating in training off the coast of Bali. Navy officials worry the vessel has dived too deep to reach or recover in time.
"We will maximize the effort today, until the time limit tomorrow at 3 a.m.," military spokesperson Maj. Gen. Achmad Riad told reporters.
A fleet of 24 Indonesian ships and a patrol plane scoured the seas around 60 miles north of Bali for the submarine, focusing on an area where an oil slick was found after the disappearance. Singapore, Malaysia and India immediately assisted in the search effort, with other nations offering as well, according to the U.S. Naval Institute.
Navy Chief of Staff Adm. Yudo Margono said the oil could have spilled from a crack in the submarine’s fuel tank, or the crew could have released fuel to reduce the vessel’s weight so it could surface.
Australia committed a sonar-equipped warship with a helicopter to the rescue effort. An American reconnaissance plane and a second Australian ship were set to bolster the search Saturday.
The submarine is believed to be somewhere between 600 and 700 meters deep -- well below the vessel's crush depth, when the undersea pressure would be greater than what the hull can bear. However, an object exhibiting high magnetism was located at a depth of 50 to 100 meters, and officials said they hope it's the submarine.
"These two Australian ships will help expand the search area and extend the duration of the search effort," Australian Navy Rear Adm. Mark Hammond said.
Indonesia President Joko Widodo asked his people to pray for the crew’s safe return while ordering all-out efforts to locate the submarine.
"Our main priority is the safety of the 53 crew members," Widodo said in a televised address Thursday. "To the family of the crew members, I can understand your feelings and we are doing our best to save all crew members on board."
The cause of the disappearance remains uncertain, with navy officials speculating that an electrical failure could have disrupted the submarine’s operations.
The Associated Press contributed to this report.