Indonesian authorities are leading a search for one of the country’s navy submarines that went missing Wednesday with 53 people on board as it was conducting a torpedo drill.
Reuters reported that the sailors aboard the German-made submarine, KRI Nanggala-402, were preparing for a weapons training exercise in waters north of the Indonesian island of Bali.
The news agency noted that authorities began searching for the submarine after it failed to send back results from the military drill.
Julius Widjojono, the first admiral of Indonesia’s navy, confirmed to Agence France-Presse that the submarine could not be reached starting at 3 a.m. local time Wednesday.
Indonesia’s defense ministry said that an initial aerial search found an oil spill near the submarine’s dive location.
Authorities have sent out two navy vessels with sonar capability to aid in the search, with the defense ministry adding that Australia, Singapore and India have responded to requests for assistance, according to Reuters.
Authorities and military analysts said Wednesday that it may be too early to determine exactly what happened to the submarine. CNN Indonesia reported that Widjojono said he suspected that the vessel had traveled to a depth of anywhere from 600 to 700 meters, or roughly 1,968 to 2,296 feet.
An Indonesian defense spokesman told Reuters that military chief Hadi Tjahjanto will hold a news conference with updated information on the search efforts on Thursday local time.
Reuters noted Wednesday that Indonesia, which has been seeking to modernize its aging defense technologies, has had several deadly accidents in recent years with military equipment.
In 2015, an Indonesian military transport plane crashed into a residential area just after takeoff, which resulted in the deaths of more than 100 people. In 2016, an Indonesian air force plane crashed into a mountain during a training exercise, killing all 13 people on board.