BUENOS AIRES — In the year since 44 Argentine sailors vanished aboard a submarine, some relatives of the missing crew members had refused to speak of their loved ones in the past tense as they held out hope for a miracle — or at least clarity as to what befell them.
This weekend, Argentine officials said the wreckage of the submarine had been found, offering the first concrete answers about one of the deadliest and most confounding maritime disasters in modern times.
“If we had a speck of hope, now there is none left,” said Gisela Polo, the sister of Esteban Alejandro Polo, 32, one of the sailors who died. “We’ve seen the images. They described the depth where it was found. It makes no sense to keep talking about him as if he were still alive.”
The discovery of the submarine, almost a year to the day after it disappeared in stormy weather, revealed that it imploded close to the ocean floor, officials said on Saturday, but that its main hull appeared to be whole. Now the government of President Mauricio Macri will have to answer questions from frustrated families about what more can be gleaned from the wreckage.
The disappearance of the submarine had confounded experts and had drawn attention to the dilapidated state of Argentina’s armed forces. Relatives of the missing sailors decried the military as reckless.
“This is news that fills us with enormous pain,” Mr. Macri said in a recorded message Saturday night in which he announced three days of national mourning. “Now we’re opening a period of serious investigations to find out the whole truth.”
Ocean Infinity, a Houston-based ocean-mapping company hired a few months ago, found the submarine nearly 270 nautical miles from the port of Comodoro Rivadavia in Chubut Province and about 3,000 feet under water. The company used unmanned, robotic devices to find it.
Early this year, Ocean Infinity was retained in the hope of solving another maritime mystery: the disappearance of Malaysia Airlines Flight 370, which vanished over the Indian Ocean in 2014. In that case, relatives of the missing passengers have also demanded that the airline and governments not give up on a four-year search that has cost millions of dollars and yielded few solid clues.
Argentina’s government signed a contract with Ocean Infinity that guaranteed the company $ 7.5 million if it found the submarine. The deal came after many crew members’ relatives accused the government of abandoning the search.
Dozens of them set up a makeshift camp outside the presidential palace in Buenos Aires for 52 days, demanding that a private company be hired to look for the submarine.
Navy officials said on Saturday that the relatively small area in which debris from the vessel was scattered and dents on its hull suggested an implosion caused by high pressure from the depth of the ocean.
The submarine was found in an area that was searched extensively but that is filled with canyons, making finding it difficult.
That area became a focal point after the Vienna-based Comprehensive Nuclear-Test-Ban Treaty Organization, which has sensors around the globe to monitor nuclear tests, recorded an incident deep in the ocean that was consistent with an explosion.
“This is the area where we had assigned 90 percent of probability for it to be located,” said Vice Adm. José Luis Villán, the head of the Argentine navy. He added that Ocean Infinity brought to bear unique capabilities. “All the navies looked in this area but absent the technology that this company had, we had not found it,” Mr. Villán said.
The Norwegian-flagged Seabed Constructor vessel operated by Ocean Infinity was scheduled to leave the coast of Argentina on Nov. 15, as the 60-day search contract was up and the crew was scheduled to head to South Africa in preparation for its next mission, said Oliver Plunkett, C.E.O. of Ocean Infinity. The company wanted to return in February to continue the search.
Then, as a member of the team was combing through the images they had already gathered in previous sonar sweeps, he said he had found something in the data, something worth postponing the departure by a few days and inspecting more closely.
It was the San Juan.
“The remarkable thing about it, it was literally the last thing we were going to do,” Mr. Plunkett said. “It is a truly unbelievable moment, in the last hour on the last day.”
Argentine officials had little to say regarding next steps or recovery efforts beyond the need to survey the scene more carefully.
The crew of the San Juan was last heard from on Nov. 15, 2017. During the early days of the search, the Argentine military sought assistance from neighboring countries and the United States as rescue personnel scoured the ocean in terrible weather conditions believing the crew could be alive.
After the government acknowledged in late November that the sailors were presumed dead based on the information provided by the nuclear sensors, the search fizzled and it seemed likely that the remains would never be found. But that was unacceptable to relatives, who pressed Mr. Macri’s cash-strapped government to keep looking.
Many relatives of the victims received the news in Mar del Plata, a port city where they had already gathered in the last few days to commemorate the one-year anniversary of the disappearance.
Ms. Polo, 24, said relatives were hopeful the remains would be brought to shore.
“It is what we all want, but they tell us they are still evaluating it,” she said.
Some relatives said the news, while painful, brought a measure of closure.
“I had already assumed he died,” said María Itatí Leguizamón, the 33-year-old wife of Germán Oscar Suárez, a radar operator on the vessel who was 29 when the San Juan vanished. “But I couldn’t help it. There was a part of me that kept holding on to the hope that he could still be alive. But now I know for sure and I can mourn.
“It’s strange how I feel such a mixture of happiness that they found it but also immense sadness. I just can’t describe it,” she said.
Officials did not immediately shed new light on what caused the disaster. They also did not say whether, or how soon, the submarine would be brought to shore. It also was unclear whether human remains could be identified.
Officials said they would release a report next week with more technical details about the fate of the submarine and those aboard.
The submarine disappeared during a routine trip from Ushuaia in the Patagonia region to Mar del Plata in Buenos Aires Province. Eight days later — in the midst of recovery operations that covered 186,000 square miles — the navy said an explosion had been recorded near the submarine’s last known location hours after its final communication with the military.
Vessels from Brazil, Britain, Chile, Russia and the United States, among others, combed the seas as part of the search for the German-made submarine, which had been part of Argentina’s fleet since 1985.
The loss of the San Juan led to a shake-up in the navy, including the dismissal of its top commander, Adm. Marcelo Eduardo Srur. Oscar Aguad, the defense minister, has remained in his post.
Ocean Infinity began its search on Sept. 7. Three naval officers and four relatives of crew members accompanied Ocean Infinity personnel aboard the ship. It involved “technology never before used during the localization of a submarine,” the navy said at the time.
It said the company would deploy “Autonomous Underwater Vehicles,” which are unmanned, robotic devices equipped with sonar and high-definition cameras that are not tethered to a ship. They could function to a depth of almost 20,000 feet.
Ocean Infinity said Saturday that the wreckage of the San Juan was found in a ravine during a search by five such vehicles. The devices were operated by 60 crew members on board the Seabed Constructor.
“Our thoughts are with the many families affected by this terrible tragedy,” Ocean Infinity’s C.E.O., Oliver Plunkett, said. “We sincerely hope that locating the resting place of the ARA San Juan will be of some comfort to them at what must be a profoundly difficult time.”
Mr. Plunkett said he hoped the “work will lead to their questions being answered and lessons learned which help to prevent anything similar from happening again.”