UPDATE: Argentina’s navy now say the sounds it thought could have been from its missing submarine were from a “biological” source and not the vessel. Many hoped the sounds were a sign of life from the sub, which lost contact with land five days ago. The search has now expanded into a multinational operation.

CGTN’s Joel Richards reports from Buenos Aires.

Waves over eight meters high, winds of up to 40 knots: these are the weekend conditions in which an international rescue mission searched for the missing Argentine submarine ARA San Juan.

With a crew of 44, the submarine’s last known position on Wednesday was nearly 500 kilometers from the Argentine coast. This weekend, hopes of the vessel’s survival were raised when the country’s defense ministry said it detected possible distress calls that failed to go through. But the navy has since confirmed those seven satellite phone signals did not come from the submarine, as was first thought.

Rough seas are making the search mission all the more difficult.

Navy officials say the ARA San Juan surfaced last Wednesday and the crew radioed that their vessel was suffering a battery failure. Commanders told the submarine to change route and head to Mar Del Plata, but it never made it.

Offers of help are coming from around the world, with countries including Brazil, Chile, Uruguay, the US and the UK all taking part in this search.

Outside the navy base in Mar del Plata, families are leaving messages. Among the missing crew is 35-year-old Eliana Krawczyk, Argentina’s first female submarine officer.

Crew members’ loved ones are understandably distressed.

“Out there in the water, there’s no WhatsApp, there’s no internet, there’s no ambulance. You are the firefighter, the crew and the submarine, there is nothing else,” Carlos Miguel Mendoza said. “They must have had some mishap: some piece of metal went flying, water got in, there was a fire… I don’t know. We’re also not going to find out because no matter what, if it was the submarine’s fault or the navy’s fault, they’re not going to tell us it was them. I hope this has a happy ending.”

The ARA San Juan joined Argentina’s fleet in 1985. German-built, the vessel has undergone maintenance in recent years to extend its service.

On Monday, President Mauricio Macri travelled to the sub’s base to lend his support as the search for its crew continues, across a vast southern Atlantic.