Spokesman Enrique Balbi yesterday told reporters that a US Navy P-8 Poseidon aircraft was dispatched to check an area where the noise was heard by two Argentine navy ships to help in the effort to isolate the source of the sounds.
The "noise" was heard in the South Atlantic about 360 kilometres from the Argentine coast and at a depth of about 200 meters, Balbi said.
A US Navy official familiar with the search cautioned that it was unclear whether the Argentines described the sound as something similar to tools being banged against the hull of a submarine as was previously reported.
The ARA San Juan went missing on Wednesday as it sailed from the extreme southern port of Ushuaia to the coastal city of Mar del Plata.
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More than a dozen international vessels and aircraft have joined the search, which has been hindered by stormy weather that has caused waves up to 6 meters.
In the first confirmation of a malfunction, an Argentine navy official said earlier Monday that the submarine reported a battery failure Wednesday and was returning to base when it went missing.
Although the German-built diesel-electric vessel carried enough food, oxygen and fuel for the crew to survive about 90 days on the sea's surface, the sub had only have enough oxygen to last seven days submerged, Balbi said.
At the Vatican, Pope Francis, a native of Argentina, said he was sending "fervent prayers" for the crew.
"Pray so that my husband, Fernando Santilli can return home," Jesica Gopar wrote. "He's in the San Juan submarine."
The submarine was originally scheduled to arrive yesterday at the navy's base in Mar del Plata, which is about 400 kilometres southeast of Buenos Aires.
Argentine President Mauricio Macri met with family members at the base as they waited anxiously for news about their loved ones.
"We can make up a thousand movies with happy and sad endings, but the reality is that the days pass by and not knowing anything kills you," Carlos Mendoza, the brother of submarine officer Fernando Ariel Mendoza, told The Associated Press.