Argentina's Defence Ministry says seven failed "satellite calls" that it believes came from a missing submarine were detected three days after the vessel lost contact.
- The calls lasted between four and 36 seconds
- The ministry said it was working on tracing the location of the calls
- A search of 80 per cent of the area initially targeted turned up no sign of the vessel, navy spokesperson says
The calls could be a sign the 44-strong crew of the ARA San Juan was trying to re-establish contact.
The calls lasted between four and 36 seconds in the late morning and early afternoon on Saturday (local time), the ministry said in an emailed statement.
Authorities said they could not confirm the calls came from the submarine, but said that was the working hypothesis.
The satellite communications were believed to have failed because of foul weather, a source in the defence ministry who was not authorised to speak publicly told Reuters.
It was not immediately clear what type of calls the vessel may have tried to make.
But submarines that are stricken underwater can float a location beacon known as an EPIRB to the surface that can then emit emergency signals via satellite.
The ministry said it was working on tracing the location with an unnamed US company specialised in satellite communications.
Argentina's navy said an electrical outage on the diesel-electric-propelled vessel might have downed its communications. Navy rules say submarines should surface if communication is lost.
The last confirmed location of the German-built ARA San Juan was 432 kilometres off Argentina's southern Atlantic coast early on Wednesday.
Argentina's navy has stepped up the search for the vessel.
But a storm with powerful winds and waves 6 metres high has disrupted the search efforts, navy spokesman Enrique Balbi said earlier today.
The US Navy said it was deploying a deep-sea rescue mission to Argentina from California to support the effort, with a remotely operated vehicle and two vessels capable of rescuing people from bottomed submarines set to arrive in coming days.
Pledges of help came from Chile, Uruguay, Peru and Brazil, while the United Kingdom was sending a polar exploration vessel, the HMS Protector, which British officials said should arrive on Sunday.
A search of 80 per cent of the area initially targeted for the operation turned up no sign of the vessel, Mr Balbi said.
He said the crew should have ample supplies of food and oxygen.
Conducting his weekly Angelus prayer at the Vatican, Pope Francis, an Argentinian, said the submarine crew was in his prayers.
Families hopeful 'this will end soon'
In the resort and fishing city of Mar del Plata, where the submarine had been destined to arrive before vanishing, a Catholic Mass was held in honour of the crew members.
Many family members of crew awaited news at the city's naval base.
"We're hopeful this will end soon to remain only as a bad memory," Maria Morales, the mother of crew member Luis Esteban Garcia said.
Carlos Zavalla, a navy commander, urged loved ones of crew members not to give up hope.
"So far, the only concrete thing is the lack of communication," he said on TV channel A24. "That's all."
If the search ends in tragedy, the episode could put the country's poor safety record in the spotlight, with potential political implications for President Mauricio Macri.
His centre-right government has set an ambitious target for cutting government spending and told Reuters in March that it had few funds at the ready to replace an outdated military fleet beyond buying aircraft for training pilots.