Fears were growing for the lives of 53 people on Wednesday after Indonesia’s defence ministry found oil floating in the sea above a deep-sea trench where a Navy submarine has vanished. The submarine is thought to have sunk into a trough 700 meters (2,300 feet) deep while conducting a torpedo drill, according to local reports. An aerial search found an oil spill near the submarine's dive location and two navy vessels with sonar capability have been deployed to assist the hunt, Indonesia's Defense Ministry said. The 43-year-old submarine, KRI Nanggala-402, was around 60 miles north of the resort island of Bali when contact was lost. "[The navy] is currently searching for it. We know the area but it's quite deep," First Admiral Julius Widjojono said. Singapore and Australia, who have submarine rescue vessels, have also been asked for assistance. The vessel had been cleared to dive as part of a training exercise before it failed to report back. A total of 49 crew members, its commander and three gunners are thought to be onboard.