An apparent explosion occurred near the time and place an Argentine submarine went missing, the country's navy reported Thursday — an ominous development that prompted relatives of the 44 crew members to burst into tears, and some to say they had lost all hope of rescue.

Navy spokesman Enrique Balbi said the search will continue until there is certainty about the fate of the ARA San Juan. He said evidence showed "an anomalous event that was singular, short, violent and non-nuclear that was consistent with an explosion."

'They haven't come back and they will never come back.' — Jesica Gopar, wife of missing submariner

The U.S. navy and an international nuclear test-ban monitoring organization said the "hydro-acoustic anomaly" was produced just hours after the navy lost contact with the submarine on Nov. 15.

"According to this report, there was an explosion," Balbi told reporters. "We don't know what caused an explosion of these characteristics at this site on this date."

The sub was originally scheduled to arrive Monday at the Mar del Plata Navy Base, about 400 kilometres southeast of Buenos Aires. 

Relatives of the crew who have gathered at the base to receive psychological counseling broke into tears and hugged each other after they received the news. Some fell on their knees or clung to a fence crowded with blue-and-white Argentine flags, rosary beads and messages of support. Most declined to speak, while a few others lashed out in anger at the navy's response.

"They sent a piece of crap to sail," said Itati Leguizamon, wife of submarine crew member German Suarez. "They inaugurated a submarine with a coat of paint and a flag in 2014, but without any equipment inside. The navy is to blame for its 15 years of abandonment."

Argentina Submarine

Police and soldiers form a protective circle around distraught relatives as they are escorted into the naval base on Thursday. (Esteban Felix/Associated Press)

Questions about refit

The German-built diesel-electric TR-1700 class submarine was commissioned in 1985 and was most recently refit in 2014.

During the $12 million retrofitting, the vessel was cut in half and had its engines and batteries replaced. Experts say that refits can be difficult because they involve integrating systems produced by different manufacturers and even the smallest mistake during the cutting phase of the operation can put the safety of the ship and the crew at risk.

The Argentine navy and outside experts have said that even if the ARA San Juan is intact, its crew might have only enough oxygen to be submerged seven to 10 days.

Authorities said late Wednesday that Argentine navy ships as well a U.S. P-8 Poseidon aircraft and a Brazilian air force plane would return to the area to check out the abnormal sound, which originated about 50 kilometres north of the submarine's last registered position.

Argentina map search for navy submarine

The submarine was about 430 kilometres off Argentina's southern coast when the navy lost contact with it on Nov. 15. (CBC)

The search location straddles the edge of the continental shelf, with widely varying ocean depths, some as great as 3,000 metres. Experts say the submarine could not have supported pressures that far down.

"If a submarine goes below its crush-depth, it would implode, it would just collapse," said James H. Patton Jr. a retired navy captain.

"It would sound like a very, very big explosion to any listening device."

Whatever it was, U.S. navy Lt. Lily Hinz said the sound detected "was not a whale, and it is not a regularly occurring sound."

The San Juan lost contact as it was sailing from the extreme southern port of Ushuaia. The submarine's captain had reported a battery failure.

More than a dozen airplanes and ships have been participating in the multinational search despite stormy weather that has caused waves of more than six metres. Search teams are combing an area of some 480,000 square kilometres, which is roughly the size of Spain.

Argentina Submarine

This 2014 photo provided by the Argentina navy shows the San Juan, a German-built diesel-electric vessel, docked in Buenos Aires. (Argentina Navy via AP)

U.S. navy sailors from the San Diego-based Undersea Rescue Command were also helping with the search and Britain's Ministry of Defence sent a special airplane with emergency life support pods to join the hunt, which also includes planes and ships from a dozen nations.

Hopes were buoyed after brief satellite calls were received and when sounds were detected deep in the South Atlantic. But experts later determined that neither was from the missing sub.

"They haven't come back and they will never come back," said Jesica Gopar, wife of submarine officer Fernando Santilli, choking back tears. "I had a bad feeling about this and now it has been confirmed."

With files from Reuters