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BUENOS AIRES, Argentina — Argentina's navy couldn't confirm Sunday whether seven brief satellite calls were from a lost submarine with 44 crew members on board.

"We are analyzing more closely to reliably determine that they weren't calls coming from the submarine," said Adm. Gabriel Gonzalez, chief of Mar del Plata Naval Base.

Gonzalez said the navy had intensified its aerial search off the country's southern Atlantic coast after adverse weather spurred waves up to 26 feet and made a maritime search difficult.

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The ARA San Juan, a German-built diesel-electric vessel, docked in Buenos Aires, Argentina, in 2014. Argentine navy via AP file

Navy spokesman Enrique Balbi said the low-frequency satellite signals, which were received Saturday, lasted a "few seconds" but hadn't connected with a base, partly because of the weather. The communication attempts were originally thought to have indicated that the crew was trying to re-establish contact.

On Sunday, search units were largely relying on information gathered from a British polar exploration vessel, HMS Protector, which was equipped with an underwater search probe and was following the path taken by the submarine, the ARA San Juan.

"Our thoughts remain with the crew of the ARA San Juan and their families at this time," Angus Essenhigh, commander of HMS Protector, according to a statement from Britain's Royal Navy.

The gesture has attracted attention since the nations fought a bloody war in 1982 after Argentina invaded the Falklands Islands.

Gonzalez also confirmed that the U.S. Navy's Undersea Rescue Command had been deployed to the search area, along with aircraft from Argentina, Brazil and the United States, as well as 11 surface vessels.

Among the 44 crew members is Eliana Krawczyk, the first female submarine officer in Argentina.

Authorities said the submarine left the extreme southern port of Ushuaia on Wednesday and lost contact as it was heading to Mar del Plata, a city on the country's northeastern coast.