Searchers for an Argentine submarine missing since November 15 battled gale-force South Atlantic winds while a navy spokesman held out hope that the 44 crew members may still be alive in an "extreme survival situation".
The ARA San Juan had only a seven-day supply of air when it reported its last position, according to officials.
Relatives of crew members focused on the possibility that the submarine may have been able to rise high enough in the ocean to refill its oxygen tanks at some point after its disappearance.
Argentina's official weather service ordered an alert for "intense winds of between 50 and 90km/h, with gusts," in Chubut province, the location from which search vessels were sailing.
"The bad weather conditions really are adverse," navy spokesman Enrique Balbi told a news conference.
Asked by a reporter about the chances that the crew may still be alive, Balbi left that as a possibility.
"We've been searching for 11 days but that does not remove the chance that they could still be in an extreme survival situation," Balbi said.
A sudden, violent sound detected underwater near the last known position of the 65-metre-long diesel-electric submarine suggested it might have imploded on the morning of November 15, after reporting an electrical problem and being ordered back to base.
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