Officials have found debris from an Indonesian submarine that went missing earlier this week, confirming that the vessel has sunk and probably cracked. The KRI Nanggala-402 sub disappeared off the coast of Bali on Wednesday while practicing torpedo drills, prompting a desperate search to find the 53 people aboard before their oxygen ran out. The debris found on Saturday included items brought on to the sub, including prayer mats, sponges and bottles. The Nanggala was made to resist pressure of up to 500 meters, but a sonar system signaled that it sunk down 850 meters—a depth that is sure to fracture the vessel, according to The New York Times. Admiral Yudo Mogono, chief of staff of the Indonesian Navy, said that it’s unclear what caused the Nanggala to sink.