Even military aircraft from the US had joined the search for Indonesia's missing KRI Nanggala-402 submarine on Friday, as the hours counted down to 3:00 PM EDT - when Indonesian officials said the vessel would exhaust its oxygen supply.
A US Navy patrol aircraft arrived in the search area on early Saturday.
Navy chief Yudo Margono said the retrieved items could not have come from another vessel, and the location of the debris suggests the submarine should be declared sunk.
According to Indonesian authorities, the KRI Nanggala-402, a German-made submarine, went missing during a military exercise around the Bali Strait on Wednesday.
But it now declares the submarine as officially sank with no hopes of finding any survivors.
If the submarine was still intact, officials said it would have enough oxygen to last until just 3 p.m. ET on Friday.
On Friday, the Pentagon said U.S. Defense Secretary Lloyd Austin had spoken with his Indonesian counterpart and offered additional support, which could include undersea search assets.
Kirby also said Secretary of Defense Lloyd Austin was meeting with his counterpart in Indonesia - Prabowo Subianto - to pursue other means of global assistance.
Five countries, including Australia, India, Malaysia, Singapore and the United States have sent specialized ships and aircraft to aid the Indonesian search. A second Australian warship as well as Singaporean and Malaysian rescue ships were also expected in the coming days.
"The family is in a good condition and keeps praying", said Ratih Wardhani, the sister of 49-year-old crewman Wisnu Subiyantoro.
Indonesian President Joko Widodo cancelled a visit to Banyuwangi port, where some rescue ships left earlier, to prepare for a weekend regional summit in Jakarta, officials said. An Australian frigate with sonar capability and a helicopter joined the multinational search operation on Friday.
Koh said the assumption that the submarine had 72 hours of oxygen was optimistic given the submarine's limited ability to generate oxygen due to its conventional power generation.
He had said Indonesia's hydrographic vessel was still unable to detect an unidentified object exhibiting high magnetism that was earlier detected located at a depth of 50 to 100 meters (165 to 330 feet).
The search focused on an area near the starting position of its last dive where an oil slick was found but there is no conclusive evidence so far the oil slick was from the sub. He asked Indonesians to pray for the crew's safe return while ordering all-out efforts to locate the stricken submarine.
There were also concerns that the vessel could have broken apart as it sunk to depths as low as 700 meters (2,300 feet) - well beyond the depth it is created to withstand.
Not only is that depth beyond the maximum depth of the submarine, potentially putting it at risk of a catastrophic hull collapse, but it also possibly puts it out of reach of available recovery options. It was not until a year later that search teams found the boat, where 44 crew members perished, on the bottom of the ocean at a depth of around 3,000 feet.
The cause of the sub's disappearance is still not certain.
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.