Argentina is continuing its search for a submarine that has been missing for nine days as relatives of the missing sailors fear the worst.

In the clearest sign of what may have happened to the ARA San Juan, which vanished a week ago off the coast of Patagonia, officials said a sound detected near the last known location of the submarine carrying 44 crew members is believed to have come from an explosion.

Enrique Balbi, spokesman for the Argentine navy, told reporters at a news conference Thursday that officials have found evidence showing that the abnormal sound, which was detected 30 miles north of the submarine's last-known location, was “singular, short, violent and non-nuclear” and “consistent with an explosion,” the Associated Press reported.

Balbi also said that officials do not know what caused the suspected explosion and that there is no evidence the vessel was attacked.

If the vessel remained intact, its crew would have only enough oxygen to survive submerged for a little more than a week. The submarine was supposed to arrive Monday at the Mar del Plata naval base, about 250 miles southeast of Buenos Aires.

Some family members of the lost sailors have already begun mourning.

A relative of one of the 44 crew members on the missing Argentine submarine is comforted outside Argentina's naval base in Mar del Plata, on the Atlantic coast south of Buenos Aires, on Thursday. (Eitan Abramovich/AFP/Getty Images)

“At this point, the truth is I have no hope that they will come back,” Maria Villareal, mother of one crew member, told local television on Friday morning, according to Reuters.

Itati Leguizamon, whose husband is among the missing, told reporters, “They did not tell us they were dead, but that is the logical conclusion.”

The United States, Britain, Brazil and Chile have sent teams of searchers to try to locate the vessel. The U.S. Navy has put more advanced resources into the Atlantic Ocean, including two unmanned underwater vehicles that use side-scan sonar to create images of large areas of the seafloor.

But the search has been stymied by 20-foot waves and winds near 50 mph, according to NPR.

Balbi told reporters Thursday that six teams were continuing to look for the missing submarine near the San Jorge Gulf, about 270 miles from the Argentine coast, CNN reported.

Earlier, officials were working to determine whether phone calls recorded from the area near the San Juan's last known location may have come from the vessel, the New York Times reported. But the Argentine defense minister later said the calls did not come from the submarine.

Argentine officials first learned about the noise Wednesday, Balbi told reporters. Argentine navy ships and aircraft from the United States and Brazil were then sent to check out the sound.

The Comprehensive Nuclear-Test-Ban Treaty Organization, based in Vienna, also said Thursday that two of its hydroacoustic stations detected an “unusual signal” near the submarine's last known location.

The signal was detected at 1:51 p.m. Greenwich Mean Time (8:51 a.m. Eastern) on Nov. 15, when Argentine officials lost contact with the San Juan, the organization said.

Hydroacoustic stations are part of the organization's monitoring system that keeps track of signs of nuclear explosions around the globe.

The news of a possible explosion drove some family members at the base to tears, according to the AP. Photos show relatives of crew members hugging and consoling each other. Some can be seen collapsing to the ground.

Others responded with anger.

“They sent a piece of crap to sail,” Leguizamon, the wife of submarine crew member German Suarez, told the AP. “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.”

The German-built diesel-electric submarine joined the Argentine navy fleet in 1985 and was upgraded a few years ago.

Cleve R. Wootson contributed to this article.