Argentina's navy announced Thursday that the search for a missing submarine that has been lost for 15 days will continue but the rescue part of the mission is over, reflecting the faded hopes for finding the 44 crew members alive.

Navy spokesperson Enrique Balbi said the rescue mission had "extended for more than twice what is estimated for a rescue."

Hopes of finding survivors had already dimmed because experts say the crew only had enough oxygen to last up to 10 days if the sub remained intact under the sea. The navy also said that an explosion occurred near the time and place where the ARA San Juan sub went missing on Nov. 15.

More than a dozen countries are still searching for the submarine which went missing on the South Atlantic on a patrol.

Navy spokesman Enrique Balbi said the rescue mission had "extended for more than twice what is estimated for a rescue."

"We've had 28 ships, nine aircraft, 4,000 people involved, 18 countries supporting," he told reporters. "Despite the magnitude of these efforts, we've been unable to find the submarine."

Balbi said the search was no longer considered a rescue mission, but the hunt would go on for the missing sub.

Some relatives of the crew broke into tears after they received the news.

Argentina Submarine

This undated photo provided by the Argentine navy shows the ARA San Juan, which has been missing for 15 days. The navy says it will continue to search for the missing submarine, but rescue efforts are done. (Argentina Navy via Associated Press)

"I don't understand this arbitrary and unjustified decision," Luis Tagliapietra, the father of 27-year-old crew member Alejandro Tagliapietra, told local TV. "It's unusually cruel. Every day, it's a new blow. I'm destroyed."

The navy has said the vessel's captain reported that water entered the snorkel and caused one of the submarine's batteries to short circuit. The captain later communicated by satellite phone that the problem had been contained, the navy says.

Some hours later, an explosion was detected near where the San Juan was last heard from. A navy spokesperson said this week that the blast could have been triggered by a "concentration of hydrogen" caused by the battery problem reported by the captain.

Millions of kilometres flown, searched

The search for the San Juan has employed some of the latest technology in one of the largest efforts of its kind. So far, aircraft have flown some one million kilometres, while ships have searched more than two million kilometres in the frigid South Atlantic, the navy said.

The U.S. navy said Thursday that a cable-operated unmanned recovery vehicle had been deployed to join the search efforts after Argentina shifted its focus to undersea assets capable of deep seafloor searches.  

Some family members have also denounced the age and condition of the vessel. President Mauricio Macri has promised a full investigation. 

The San Juan, a German-built diesel-electric TR-1700 class submarine, was commissioned in the 1980s and was most recently refitted in 2014.

At the sub's home naval base in Mar del Plata, relatives were hit hard by Thursday's announcement. Some hugged and fell on their knees sobbing near a fence crowded with blue-and-white Argentine flags, rosary beads and messages of support. Others took to social media to pay homage to their loved ones.

"I stay with this image," Jesica Gopar, said in a tweet that included a photo of her husband, submarine officer Fernando Santilli, smiling and holding their young son in his arms. 

"He's the most beautiful being that God could have put on my path 13 years ago," she wrote. "He's a hero who must be recognized along with his 43 other crew members. I hope you didn't suffer my love."