The Argentine navy has detected what appeared to be seven satellite messages sent from a missing submarine, but communication with the vessel was never established, and its whereabouts in the south Atlantic remained a mystery late Saturday.
The 44-crew submarine, the subject of an intensive search involving eight nations, had been out of contact since Wednesday morning. The first indication of leads to its whereabouts came Saturday night when Defense Minister Oscar Aguad said over Twitter that the Argentine military had detected what he called "communication attempts."
Later, the Argentine navy tweeted that it appeared that the crew of the ARA San Juan had attempted to establish contact but was unable to do so. The seven satellite messages lasted from 4 to 36 seconds. The first occurred at 10:52 a.m. and the last at 3:42 p.m., the navy said.
The navy was still working to establish whether the messages did indeed come from the submarine. It also was unclear whether the vessel was at the surface or underwater.
The submarine had participated in naval exercises off southern Argentina before departing Monday from the city of Ushuaia for a naval base in Mar de Plata. The last contact was made after the northbound vessel passed the Valdes Peninsula about 270 miles off Argentina's coast.
NASA joined the search effort on Saturday with a P-3
Argentine naval officials said they received no distress signals from the vessel, a German-built TR-1700 model, before losing contact. Vessels from Chile, Brazil, Peru, Uruguay, South Africa and the United Kingdom are also assisting in the search.
Pope Francis, a native of Argentina, said in a statement issued by the Vatican earlier Saturday that he was praying for the safe return of the submarine and its crew, and for "spiritual serenity and Christian hope" for Argentina. He said he felt especially close to family members "in these difficult moments."
Anguished family members of the crew have gathered at the Mar de Plata base awaiting news.
"It's agonizing the passing of the hours, a mixture of horrible feelings and silence," said Marcela Moyano, wife of submarine machinist Hernan Rodriguez, in an interview at the base with TodoNoticias TV channel before Aguad's announcement. "It's a situation of desperation and fear. But we're still hopeful they are returning."
Of the 44 crew members, one is a woman: Lt. Eliana Maria Krawczyk, 34, the sub's operations chief. Her father, Eduardo, said in a TV interview Thursday that he last talked to his daughter two weeks ago.
"She told me that after arriving at Tierra del Fuego, that the [female] governor of the state came aboard the submarine and congratulated her because a woman was on the crew," Eduardo Krawczyk said. He added that he is praying for his daughter's safe return and that their union will be like "being born again."
Psychologists and a Roman Catholic bishop have arrived at the naval base to counsel family members. Navy spokesman Enrique Balbi said the fleet was "not discarding any hypothesis" on what might have happened to the sub.
"We are going to suppose the submarine had problems of communications, that there might have been a blackout, or power failure, and that it is now adrift," Balbi said. "From [projected] movement after going adrift, we can estimate the search area."
One of three submarines in the Argentine fleet, the diesel-powered sub measures 220 feet long and has a range of 13,000 miles. It underwent a major overhaul and reconditioning in 2008 that officials here say qualified it for 30 years more of use.
But weather in the search area has turned rough, with strong winds and waves as high as 20 feet, complicating the rescue operation, Balbi said.
"Remember that the part of the submarine that is above surface is very small, just a third of its length. The color of the vessel doesn't help either because it mimics that of the ocean," Balbi told reporters.
Argentine President Mauricio Macri said in a message Friday over Twitter that the government is using all resources at its disposal to search for the submarine. Officials are in contact with the crew's family members to keep them informed, he said.
"We share your worries and those of all Argentines," Macri wrote.
Four Argentine ships, various helicopters and 500 marines are participating in the search. Aguad, the defense minister, said the country is accepting all offers of international assistance. The United Kingdom has lent assets including a Hercules C-130 military aircraft based in the Falkland Islands, over which the U.K. and Argentina fought a war in 1982.
Special correspondents D'Alessandro and Kraul reported from Buenos Aires and Bogota, Colombia, respectively.
8:25 p.m.: This article was updated with details about the communication attempts.
5:30 p.m.: This article was updated to report the crew of the missing submarine has attempted to communicate.