Argentina's navy on Monday picked up what could be noises from the country's missing submarine and said the sub's captain reported a "failure" in the vessel's battery system before it disappeared.
The sonar systems of two ships detected noises sounding like tools being banged against the hull of a submarine, according to a senior US Navy official familiar with the Navy's assistance in the search for the vessel.
The official said that crews of submarines in distress bang on the vessel's hull to alert passing ships to their location. The missing submarine -- the ARA San Juan -- has a crew of 44.
The Argentinian navy was able to fix the rough location of the sounds and is now concentrating its search in an area of 35 square nautical miles approximately 330 miles off the coast of Argentina, the official said.
The submarine was heading from a base in southern Argentina's Tierra del Fuego archipelago to its home port in Mar del Plata. It was scheduled to arrive there Sunday.
'Failure' reported in the vessel's battery system
The vessel's captain reported a "failure" in the vessel's battery system shortly before it disappeared last week, the country's Navy spokesman Gabriel Galeazzi said Monday.
After he reported the sub had experienced a "short circuit," he was told to "change course and return to Mar del Plata," said Galeazzi.
This type of damage is considered routine and the vessel's crew was reported safe, he added.
The Argentinian navy had one more communication with the captain before the sub went missing, said Galeazzi. The navy did not give details of the content of that final communication.
On Saturday, seven reported communication attempts were initially believed to originate from the San Juan -- but on Monday officials said the radio calls had not come from the missing sub.
The last confirmed contact with the submarine was Wednesday, the navy said.
A US Navy P-8A Poseidon aircraft, also known as a submarine hunter, is now assisting in the search area.
The US official said that the waters of the Atlantic Ocean where the sounds originated are extremely deep. The official stressed that search efforts thus far have yet to locate the submarine.
The Argentinian military has also been working with a US company that specializes in satellite communication to determine the location of the submarine.
The search area, off the Patagonia coast, is notorious for strong storms.