Indonesian Navy Chief Yudo Margono, front left, Indonesian Military chief Hadi Tjahjanto, center, and Indonesia police chief Listyo Sigit Prabowo, right, talk to media as they display debris found in the waters during a search for the Indonesian Navy submarine KRI Nanggala at Ngurah Rai Military Air Base in Bali, Indonesia Image Credit: AP

Indonesian authorities has found debris in the area where a missing Navy submarine was last reported to be located.

"We believe it belongs to the submarine and would not have floated to the surface if the submarine had not cracked under intense pressure," Commander Yudo Margono told a press conference in Bali island on Saturday.

The KRI Nanggala-402 had 53 crew members onboard when it disappeared in waters off Bali on Wednesday during a training exercise. Authorities had predicted the oxygen in the vessel would be depleted by 3 a.m on Saturday.

"The 72-hour window has passed for the availability of oxygen," Military Chief Hadi Tjahjanto said at the press conference.

Among the debris found was a bottle of grease used to lubricate the periscope, which is kept at hand by crew members in case it's needed, Tjahjanto said.

Scouring waters

Some 20 vessels and five aircraft are scouring the waters in search of the submarine, and more have been dispatched by the governments of Singapore, Malaysia, Australia and India.

Authorities believe the German-made Nanggala sank to a depth of more than 700 meters (2,300 feet). The submarine, which at more than 40 years old is among the world's oldest in service, was not built to withstand pressure beyond 230 meters, said Ridzwan Rahmat, principle defense analyst at Janes.

Missing Indonesian submarine was old, overloaded, analyst says

Indonesia has five submarines in total. The government has been trying to revitalize its military equipment and has selected the defense ministry as one of the biggest recipients of the last few years' budget funds to achieve that target.

Indonesia set aside 1.3 trillion rupiah ($89.5 million) in this year's budget for shipbuilder PT PAL Indonesia to improve its submarine-making capacity and help reduce the country's dependence on foreign-made military equipment.

Frans Wuwung, a retired navy admiral and former chief of Nanggala's engine room, said he believed the submarine was in a fit condition before embarking on the exercise despite its age.

"There are rigid requirements in place and the submarine would not have obtained the clearance to dive if it had not ticked all the boxes," Wuwung said by phone on Saturday.

There is no deadline for the search and the military will continue looking until they find the missing vessel, "whatever the result is," Djawara Whimbo, a military spokesman, said.