BUENOS AIRES (Reuters) - Searchers for an Argentine submarine missing since Nov. 15 battled gale-force South Atlantic winds on Sunday while a navy spokesman held out hope that the 44 crew members may still be alive in an “extreme survival situation.”

Slideshow ( 2 images )

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 90 kilometers per hour (31 and 56 mph), 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.

The U.S. Navy’s Undersea Rescue Command sent a ship from Chubut’s port Comodoro Rivadavia on Sunday, outfitted with a remotely operated mini-sub to be used as a rescue vehicle if the San Juan is found. The ship was expected to reach the search zone some 430 kilometers (267 miles) off Argentina’s southern coast by Monday afternoon.

A sudden, violent sound detected underwater near the last known position of the 65-meter-long (213 feet) diesel-electric submarine suggested it might have imploded on the morning of Nov. 15th, after reporting an electrical problem and being ordered back to base.

Oscar Vallejos, a naval veteran and father of San Juan crew member Celso Vallejos, told local television that he refused to believe his son would not return alive.

“Hope always high,” said the burly Vallejos, his posture ramrod straight and eyes hidden behind sunglasses.

A black baseball-style cap identified him as a navy war veteran.

Other crew family members were less sure.

“We are in a state of total uncertainty,” Maria Victoria Morales, mother of Luis Garcia, an electrical technician aboard the missing Cold War-era submarine, told Reuters by telephone.

A Russian plane arrived in Argentina on Friday carrying search equipment capable of reaching 6,000 meters (20,000 feet) below the sea surface, according to the Argentine navy.

The international search effort includes about 30 ships and planes manned by 4,000 personnel from 13 countries including Brazil, Chile and Great Britain.