Update 2.50pm: Argentina says a sound detected in the search for a missing submarine with 44 crew members on board is consistent with a non-nuclear explosion but say that there is no evidence of an attack.
Navy spokesman Enrique Balbi said the relatives of the crew have been informed and that the search will continue until there is full certainty about the fate of the ARA San Juan.
Ships and planes have returned to a search area to check on the noise that experts say could provide a clue to the vessel's location.
US and specialist agencies say the "hydro-acoustic anomaly" was produced just hours after the navy lost contact with the submarine on November 15.
Experts worry that if the ARA San Juan is intact but submerged, its crew might have only enough oxygen to last seven to 10 days.
Update 8.15am: Argentina reports new clue in search for missing submarine
Ships and planes hunting for a missing Argentine submarine with 44 crew members will return to a previously searched area after officials said that a noise made a week ago in the South Atlantic could provide a clue to the vessel's location.
The Argentina navy spokesman, Captain Enrique Balbi, said the "hydro-acoustic anomaly" was determined by the United States and specialist agencies to have been produced on November 15, just hours after the final contact with the ARA San Juan and could have come from the sub.
The sound originated about 30 miles north of the submarine's last registered position, he said.
"It's a noise. We don't want to speculate" about what caused it, Balbi said.
He said Argentine navy ships as well as a US P-8 Poseidon aircraft and a Brazilian air force plane would return to the area to check out the clue, even though the area was already searched.
On land, relatives of the submarine's crew grew increasingly distressed as experts said the vessel lost for seven days might be reaching a critical period of low oxygen.
The San Juan went missing as it was sailing from the extreme southern port of Ushuaia to the city of Mar del Plata, about 250 miles southeast of Buenos Aires.
The Argentine navy and outside experts worry that oxygen for the crew would last only seven to 10 days if the sub was intact but submerged. Authorities do not know if the sub rose to the surface to replenish its oxygen supply and charge batteries, which would affect the calculation.
The German-built diesel-electric TR-1700 class submarine was scheduled to arrive on Monday at the naval base in Mar del Plata, where city residents have been dropping by with messages of support for relatives of the crew.
More than a dozen planes and ships are participating in the multinational search, despite stormy weather that has caused waves of more than 20 feet. Search teams are combing an area of some 185,000 square miles, which is roughly the size of Spain.
President Donald Trump went on Twitter to offer his good wishes to Argentina on Wednesday, though he inflated the number of missing sailors by one.
"I have long given the order to help Argentina with the Search and Rescue mission of their missing submarine. 45 people aboard and not much time left. May God be with them and the people of Argentina!" his tweet said.
Hopes were lifted after brief satellite calls were received and when sounds were detected deep in the South Atlantic. But experts later determined that neither was from the missing sub. A US Navy aircraft later spotted flares and a life raft was found in the search area, but authorities said neither came from the missing submarine.
The navy has said the submarine reported a battery failure before it went missing. Authorities have no specific details of the problem.