A distress signal detected Monday by Argentina’s navy may have come from a missing military submarine. The ARA San Juan has been missing since Wednesday with 44 crew members on board.

The submarine’s last known location was off the coast of Puerto Madryn in southern Argentina. The craft had previously left the city of Ushuaia to head toward a naval base at Mar del Plata.

Sonar systems detected what sounded like tools being banged against the hull of a submarine, CNN reported, citing a senior United States Navy official. A search team was deployed to scour some 35 square miles about 330 miles off the coast of Argentina.

The submarine experienced a routine technical failure in its battery system before it vanished, according to Navy spokesman Gabriel Galeazzi. Such mechanical problems are not uncommon and numerous backup systems are in place should such an incident occur, Galeazzi said.

“The vessel surfaced and it reported a breakdown,” Galeazzi said. “It was therefore asked to change course and go to Mar del Plata.”

The navy had one additional communication with crew on the submarine but it remained unclear what the contents of the last conversation were. Previous reports suggested there had been a power outage and a fire on the ship, according to Naval Today. Officials refuted other reports that said the submarine was found and was being towed to safety.

Numerous aircraft and ships were deployed from the United States, Britain, Argentina, Chile and Brazil to search for the submarine in previous days. The U.S. Navy was also involved in the search and sent a crew consisting of four aircraft and a “submarine rescue chamber” equipped to rescue up to six people at a time, NBC News reported.

Authorities said the ship had enough food to continue on its journey to Mar del Plata but it was unclear how long the submarine could stay underwater. Officials said if the craft was intact but sunk, crew would have a week to 10 days of oxygen, but much depends on other circumstances, according to CNN.

“It’s dependent upon the last time they actually recharged their batteries, how long ago they refreshed the air, what’s inside the submarine,” former U.S. Navy diver and submariner William Craig Reed told CNN.