The ARA San Juan, which has 44 crew members, lost contact in the South Atlantic last Wednesday.
An Argentine naval officer told journalists that the sub had reported a breakdown and had surfaced.
Frank Owen, from the Submarine Institute of Australia, told news.com.au that the crew could still be underwater and hoping they are brought to the surface.
The ARA San Juan had been traveling from a base in the Tierra del Fuego archipelago to its home base in Mar del Plata, a city hundreds of miles to the northeast.
As The New York Times reports, "From December to April, the high season for fishing, as many as 450 fishing boats from China, South Korea, Taiwan and Spain flock to the area to dredge up Argentine shortfin squid, said Milko Schwartzman, a marine conservation expert who has studied the trade".
The ARA San Juan, a TR-1700-class diesel-electric submarine that was originally constructed in Germany during the 1980s, was last heard from on November 15 and carries a maximum 7 day supply, meaning the supply is likely to run out sometime on Wednesday. The navy did not give any additional details of the content of that interaction however. Each time we are entering little by little a critical period'. It has a seven-day supply of oxygen. For now, based on the color, they don't belong to the submarine, ' Balbi said.
Reports: Object spotted on ocean floor in hunt for missing submarine
The US Navy was preparing on Tuesday to deploy rescue equipment, including a remote-operated vehicle.
A separate rescue vessel also reported hearing an infrasound sonal signal late last night, though neither signal has been confirmed as the ARA San Juan as of yet. "We welcome the help we have received to find them".
The 34-year-old German-built submarine - which was refitted between 2007 and 2014 - had flagged a breakdown in its batteries.
A total of 49 ships and aircraft from Argentina, the U.S., the UK, Brazil, Chile and other countries were taking advantage of improved weather conditions to search an area larger than the state of California. If the vessel is resting on Argentina's continental shelf, it is likely in waters shallower than this, but if it's farther out into the Atlantic Ocean, it could be below its "crush depth" in which the hull buckles under pressure.
Video showing the severe weather facing sea rescuers was posted on Twitter, capturing huge waves battering the fleet of ships helping the search.
It was thought sounds detected by a search vessel in the area resembled objects being smashed against a submarine's hull, but hope it came from the missing vessel was dashed after analysis found the noise wasn't metallic. But the raft is a different model than what would be carried on the San Juan, and a white flare is not typically used by the crew.
'Rampage' Trailer: 'San Andreas' Team Back In Action, Animal Style
Warner Bros has released the first trailer for Rampage , the arcade game film adaptation we did not realise we needed. The gene-editing bomb causes George, a wolf and a crocodile to sprout, gaining height and mass - but that's not all.