BUENOS AIRES — Argentina’s Navy detected seven brief satellite calls late Saturday that officials believe might have come from a submarine with 44 crew members that hadn’t been heard from in three days.
The communication attempts ‘‘indicate that the crew is trying to re-establish contact, so we are working to locate the source of the emissions,’’ the Navy said on its Twitter account. ‘‘The calls of a short duration, between 4 and 36 seconds, were received between 10:52 and 10:42 on Saturday at different bases.’’
Argentina’s authorities clarified that it has not been confirmed that the calls came from the submarine, though that is the working hypothesis.
Earlier Saturday, Navy spokesman Enrique Balbi said the area being searched off the country’s southern Atlantic coast had been doubled as concerns about the fate of the submarine and its crew grew.
‘‘We are not discounting any hypothesis,’’ Balbi said. Possibilities to explain its disappearance include ‘‘a problem with communications’’ or with its power system, he said.
Authorities last had contact with the German-built diesel-electric sub, the ARA San Juan, on Wednesday as it was on a voyage from the extreme southern port of Ushuaia to Mar del Plata.
President Mauricio Macri said in a tweet that the country will use ‘‘all resources national and international that are necessary to find the submarine.’’
Pledges of help came from Chile, Uruguay, Peru, and Brazil, as well as the United States, which sent a NASA scientific aircraft and a Navy plane. Britain was sending a polar exploration vessel, the HMS Protector, which British officials said should arrive Sunday.
The US Navy ordered its Undersea Rescue Command based in San Diego, Calif., to deploy to Argentina to support the search for the submarine.
Admiral Gabriel Gonzalez, chief of the Mar del Plata Naval Base, said they are coordinating ‘‘with units from the United Kingdom and the United States.’’ Britain and Argentina fought a war in 1982 over the Falkland Islands, which are called the Malvinas in Argentina.
Relatives of the crew members gathered at the Mar del Plata Naval Base in the hopes of hearing news about their loved ones.
‘‘We feel anguish. We are reserved but will not lose our hope that they will return,’’ Marcela Moyano, wife of machinist Hernan Rodriguez, told television network TN.
From the Vatican, Argentine Pope Francis said he was making ‘‘fervent prayers’’ for the crew.
Francis ‘‘asks that his closeness be conveyed to their families and to the military and civil authorities of the country in these difficult moments.’’
Those family members and the Argentine government were facing a cruel fact of submarine life. The vessels are often among a country’s most expensive and complex military assets — and, during accidents or times of crisis, their most vulnerable.
