Water entered the snorkel of the Argentine submarine ARA San Juan, causing its battery to short-circuit before it went missing on Nov. 15, a navy spokesman said on Monday as hope dwindled among families of the 44-member crew.

The San Juan had only a seven-day oxygen supply when it lost contact, and a sudden noise was detected that the navy says could have been the implosion of the vessel. Ships with rescue equipment from countries including the United States and Russia were nonetheless rushing to join the search.

Before its disappearance, the submarine had been ordered back to its Mar del Plata base after it reported water had entered the vessel through its snorkel, causing a battery short circuit, navy spokesman Enrique Balbi told a news conference.