MAR DEL PLATA, Argentina — Argentina’s president said Friday an international search will continue for a submarine carrying 44 crew members that has been lost in the South Atlantic for nine days and that the sub’s disappearance will be investigated.

The Argentine navy says an explosion occurred near the time and place where the submarine went missing on Nov. 15 as it was sailing from the extreme southern port of Ushuaia to the coastal city of Mar del Plata. That’s led some family members of the crew to give up hope of a rescue. Navy officials and outside experts also worry that even if the sub is intact but submerged, its crew may be running out of oxygen.

“The disappearance and current search of the ARA San Juan submarine has touched all Argentines. It’s a difficult moment for all, but obviously, especially for the families of the 44 crew members,” President Mauricio Macri said in his first public comments about the missing sub at the navy’s headquarters in Buenos Aires.

“I’m here to guarantee you that we will carry on with the search, especially now that we have the support of all the international community.”

More than a dozen airplanes and ships have been participating in the multinational search across an area of some 185,000 square miles (480,000 square kilometers), which is roughly the size of Spain.

The Argentine navy said Friday that Russia is sending an Antonov transport aircraft, and a ship in the southern Patagonian port of Comodoro Rivadavia is being adapted to carry a U.S. Navy submarine rescue chamber. They will focus the search efforts on a smaller area where the explosion was recorded.

The ARA San Juan, a German-built diesel-electric TR-1700 class submarine, was commissioned in 1985 and was most recently refitted in 2014.

“No one goes out to sea knowing that they can lose their life,” said Ramon Francisco Escobar, who was part of the crew that first brought the sub from Germany to Argentina in 1985. “It was a reliable submarine.”

The sub was originally scheduled to arrive Monday to a navy base in Mar del Plata, about 250 miles (400 kilometers) southeast of Buenos Aires. Local residents prayed for the crew’s return during a religious ceremony and later sang Argentina’s national anthem outside the base Friday. Some relatives of the crew who have gathered there fear that their loved ones will no longer be rescued.

“Hope is the last thing you lose. I’m waiting for a surprise, but I’m not really counting on it,” Luis Tagliapietra, father of 27-year-old crew member Alejandro Damian Tagliapietra, told The Associated Press.

“You go from denial to suffering, from optimism to pessimism,” he said, holding back tears. When he found out about the explosion from his son’s direct superior, he was told that there was a possibility there were no survivors.

“I asked them if they were all dead, and he said: ‘Yes.'”

Some family members have denounced the navy’s response to the disappearance and the condition of the 30-year-old vessel.

Although Macri said that it’s not the time to point fingers at anyone, he promised a probe of the sub’s disappearance.

“This demands a serious, deep investigation,” Macri said. “We need to understand how a submarine that had undergone a midlife refit, and that was in perfect conditions to sail, suffered this explosion.”

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Henao reported from Buenos Aires, Argentina. Associated Press writers Mayra Pertossi and Victor Caivano, and video journalist Paul Byrne contributed to this report.