The submarine went missing nine days earlier with only a one-week supply of oxygen onboard. The navy vowed to keep searching for the vessel and declined to confirm the wide-held fear that the crew had died.

“Until we find the submarine and know the facts, we cannot venture to say anything more one way or the other to the families,” navy spokesman Enrique Balbi said.

“The search is very difficult,” he said.

Relatives of the crew had arrived at Mar de Plata on Monday, filled with an optimism that had all but disappeared by Friday.

“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.

Others said they would remain at Mar del Plata.

“I‘m at the base and I‘m going to stay until they find the submarine,” Silvina Krawczyk, sister of the sub’s only female officer, Eliana Maria Krawczyk, told Reuters through the WhatsApp messaging application.

Around 30 boats and planes and 4,000 people from Argentina, the United States, Britain, Chile and Brazil have joined the search for the submarine, which last transmitted its location about 480 km (300 miles) from the coast.

Some family members accused the navy of putting their loved ones at unnecessary risk by sending them out in a more than 30-year-old vessel that they suspected was not properly maintained, an accusation the navy has denied.

“They killed my brother!” a man leaving the base in a car shouted out to reporters. The older man driving the car was crying.

The submarine, called the San Juan, was launched in 1983 and underwent maintenance in 2008 in Argentina. The armed forces have had to face dwindling resources and lack of training since the end of a military dictatorship in the early 1980s.

A sound detected underwater on the morning of Nov. 15, around the time the San Juan sent its last signal and in the same area, was “consistent with an explosion,” navy spokesman Balbi said on Thursday.

The information about the possible explosion came from the Comprehensive Nuclear Test-Ban Treaty Organization, an international body that runs a global network of listening posts designed to check for secret atomic blasts.

The fury of the crew’s relatives was aimed more at the navy, which they say has kept them in the dark about the missing vessel, than at President Mauricio Macri. Both the submarine program and military budget cuts started long before Macri’s late 2015 election. He has enjoyed generally favorable coverage from major Argentine news media outlets as he pushes free-market reforms.

The government promised a thorough investigation into the sub’s disappearance and the navy’s response.