By Jason Hanna, Natalie Gallón and Laura Smith-Spark, CNN

    (CNN) -- The Argentine navy says it's not ready to give up a search for a vanished submarine, after the military revealed a sound consistent with an explosion was detected near the vessel's last known location last week off the country's South Atlantic coast.

"We keep searching ... no country will say at this moment until when," Argentine navy spokesman Enrique Balbi told reporters Friday in Buenos Aires. "Obviously, it's something finite in time, but we are not talking about this at the moment."

Crews from a dozen nations have been searching by air and sea for the ARA San Juan, which has 44 crew aboard and was last contacted off the coast of Argentina on November 15.

Chances of finding the crew with a viable air supply may be dwindling.

The San Juan, if intact after an initial emergency, would have enough air to last seven to 10 days, if it remained fully immersed during that time, experts say. If the submarine has surfaced or "snorkeled" -- that is, raised a tube to the surface to refresh the vessel's air -- the crew may have bought more time.

Balbi's latest comments come a day after he announced that a noise "consistent with an explosion" had been registered November 15, near where the sub was last known to be.

The news was sorely received by relatives of the San Juan crew members. After Argentine officials briefed the relatives Thursday at Argentina's Mar del Plata navy base, some family members appeared overcome with grief, sobbing and holding each other up outside the facility.

On Friday, Balbi said he wouldn't entertain speculation about where the San Juan is, despite knowing roughly where the noise came from.

"We still do not know where (the sub) is," he said.

 The noise

 The submarine was traveling last week from a base in Argentina's far southern Tierra del Fuego archipelago to its home base in Mar del Plata, on the northern side of the country.

The Argentine navy lost contact with the San Juan shortly after the vessel's captain reported a failure in the battery system while the sub was submerged off Argentina's South Atlantic coast, the military said.

On Thursday, Balbi announced that the navy recently had learned that "an anomalous, singular, short, violent and non-nuclear event, consistent with an explosion, was registered" near the sub's last known location on November 15.

Balbi said information about the noise had first been given to Argentina on Wednesday by the United States.

In addition, the Comprehensive Nuclear Test-Ban Treaty Organization, or CTBTO, based in Vienna, Austria, informed Argentina on Thursday that its monitoring systems had detected an unusual sound.

On November 15, it said, "two CTBTO hydroacoustic stations detected an unusual signal in the vicinity of the last known position of missing Argentine submarine ARA San Juan."

The sound of "an underwater impulsive event" was detected at 1:51 p.m. GMT (10:51 a.m. local time) by its underwater microphones, it said. The organization is set up to monitor compliance with the proposed nuclear test ban treaty and has 11 hydroacoustic stations positioned around the world listening for signs of nuclear explosions.

"Details and data are being made available to the Argentinian authorities to support the search operations that are underway," the organization said.

Balbi said teams have been searching for the missing submarine in waters of the San Jorge Gulf, about 430 kilometers (268 miles) from the coast. The depth of the ocean varies considerably there, ranging from 200 to 2,000 meters, he said.

There was no evidence of any attack and no information on the cause of the noise, Balbi said.

About 4,000 people are involved in the search, he said.

Distraught families

Distraught families took Thursday's news hard. They had been gathering for days at the Mar del Plata base for news of their loved ones.

Maria Itatí Leguizamón, the wife of one of the crew members, told CNN en Espanol that she assumes crew members are dead -- and thinks the military has believed the same for some time.

"They did not tell us that they are dead, but this is a logical assumption," she said Thursday. "These (expletive) knew it. They did not give an explanation. They said that according to them, they now know (about the sound), but how do they now know? How could they not know that?"

Jessica Gopar, wife of crew member Fernando Santilli, told reporters Thursday that she also believed the crew was gone.

"We don't have any saint left to pray to; we have no one left to ask. ... They did not come back, and they will never come back again," she said. "I don't know if their bodies will come back. That is what hurts the most because I will not be able to bring him a flower, I will not be able to have him at home."

"I had a bad feeling," she said. "And today it was confirmed to me."

No contact since November 15

Balbi said during a Wednesday news conference that there had been "no type of contact, not passive nor active," with the submarine since November 15 and that the search was "in the critical phase."

A spokesman for the UK Ministry of Defense confirmed Thursday that a Royal Air Force C-130 aircraft had landed in Argentina and was now a part of the search, as was a Voyager, a refueling aircraft that helps searches go on longer.

It appeared to be the first time since the Falklands conflict in 1982 that an RAF plane had landed in Argentina, although the UK Ministry of Defense would only characterize it as the first time in a "very long time." The Royal Navy's ice-patrol ship, HMS Protector, had already joined the search.

Russia had also sent navy specialists and equipment to Argentina, state news agency Tass cited the Russian Defense Ministry as saying Thursday. The deployment includes a ship equipped with two deep-water vehicles capable of searching depths of up to 6,000 meters. Balbi said Friday a Russian plane will join the search.

The US Navy has sent underwater search vehicles and two undersea rescue systems that could be used to rescue crew members.

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