The Argentine submarine that has been missing since last Wednesday reported a mechanical breakdown in its last communication, the BBC reported.

The South American country’s Defence Ministry said over the weekend that the missing vessel, named ARA San Juan, had attempted to communicate via satellite. But hopes of finding the 44 missing crew members were dashed on Monday after the Navy confirmed that the seven failed calls did not come from the vessel, Reuters reported.

“The vessel surfaced, and it reported a breakdown,” naval commander Captain Gabriel Galeazzi said, adding that there may have been a short circuit in the vessel’s batteries. Captain Galeazzi, who heads a naval base near Buenos Aires, said mechanical problems, though uncommon, rarely posed a risk.

“A warship has a lot of backup systems to allow it to move from one to another when there is a breakdown,” he was quoted as saying by the BBC.

Over a dozen boats and aircraft from Argentina, the United States, Britain, Chile and Brazil are looking for the missing submarine, though the search operations have been hampered by storms in the region.