An "abnormal" and "violent" click disturbed the South Atlantic Ocean, near the site where the Argentine submarine, which has been ignored for the last 24 hours, sent a signal for the last time.
It is noted that the submarine was carrying 44 people, whose fate is unknown so far.
The search teams cover an area of about 480.000 square kilometers, which is about the size of Spain.
Spokesman Enrique Balbi described the November 15 incident as "abnormal, unique, brief, violent" and "non-nuclear".
Rescue teams have focused their efforts on the surrounding area, which was 30 nautical miles north of the last location from which the submarine had communicated. According to U.S. Navy Lt. Lily Hinz, the sound could not be attributed to marine life or ocean noise.
"It was not a whale, and it is not a sound that appears regularly"