Rescuers in race against time to find Indonesian navy submarine | Indonesia

Rescue teams have been racing against time to find an Indonesian navy submarine lost in the Bali Sea with 53 crew, which is likely to be running out of oxygen if not already crushed by water pressure.

Search helicopters and ships left Bali and a naval base in Java heading to the area on Friday where contact was lost with the 44-year-old KRI Nanggala-402 on Wednesday as it prepared to conduct a torpedo drill, with the head of the Indonesian submarine fleet aboard.

If the submarine was still intact, officials said it would only have enough air to last until around dawn on Saturday.

“So far we haven’t found it … but with the equipment available we should be able to find the location,” Achmad Riad, a spokesman for the Indonesian military, told a news conference.

An air force pilot said six tonnes of equipment had been flown to a base to help with the search, including underwater balloons to help lift a vessel.

The navy said it was investigating whether the submarine lost power during a dive and could not carry out emergency procedures as it descended to a depth of 600-700 metres, well beyond its survivable limits.

An object with “high magnetic force” had been spotted “floating” at a depth of 50-100 metres, the Indonesian navy chief of staff, Yudo Margono, said, and an aerial search had spotted an oil spill near the submarine’s last location.

The diesel-electric powered submarine could withstand a depth of up to 500 metres but anything more could be fatal, a navy spokesperson, Julius Widjojono, said. The Bali Sea can reach depths of more than 1,500 metres.

A defence expert said the crew could still be found alive. “But if the submarine is in a 700-metre sea trough, it will be difficult for them to survive because underwater pressure will cause cracks and ruptures of the steel hull,” Connie Rahakundini Bakrie said.

The submarine joined the Indonesian fleet in 1981, the defence ministry said, and underwent a refit in South Korea that was completed in 2012. It was said to be in good condition.

“I hope they will be found alive,” said Berda Asmara, the wife of crew member Guntur Ari Prasetyo, 39, who has sailed on the Nanggala for 10 years. “We had a video call. He told me that he would go sailing and asked me to pray for him,” she said of the last time they spoke.

Natalie Sambhi, an expert on Indonesian military and security at Verve Research, said the best scenario was that the submarine was not at a great depth but even then the challenges were immense.

“When you factor in the oxygen levels for the actual number of crew and then the time it takes to locate, assessment of recovery, then engagement in that recovery that timeline looks even longer,” she said.

Australia, India, Malaysia, Singapore and the US have sent specialised ships and aircraft in response to Indonesian requests for assistance. The US military is sending a P-8 Poseidon aircraft to assist in the submarine search.

On Friday, the Pentagon said US defence secretary, Lloyd Austin, had spoken to his Indonesian counterpart and offered additional support, which could include undersea search assets.

The White House national security adviser, Jake Sullivan, told the Indonesian foreign minister, Retno Marsudi, on Thursday the “United States would do everything possible to support Indonesia’s search and rescue effort”, a spokesperson said.