Argentina’s navy on Monday detected what could be a distress signal from a missing submarine — and said its skipper reported a battery system “failure” before it disappeared last week, according to reports.

Two ships picked up noises sounding like tools being banged against the hull of a sub, said a senior US Navy official familiar with the American efforts to find the ARA San Juan, CNN reported.

The official said that crews of submarines in distress strike on the hulls to make noise that the sonar systems of passing ships can detect.

The navy fixed the rough location of the sounds the ships picked up and was focusing its search in an area of 35 square nautical miles about 330 miles off the coast of Argentina, according to CNN.

The 213-foot-long sub was heading from a base in southern Argentina’s Tierra del Fuego with 44 crew members aboard when the captain reported a malfunction on Wednesday.

“The vessel surfaced and it reported a breakdown. It was therefore asked to change course and go to Mar del Plata,” said Gabriel Galeazzi, head of the home port in the northeastern city.

The captain reported that all crew members were in perfect health, according to the BBC.