Hopes that 44 crew members of a missing Argentine navy submarine may be found alive rose after the defense ministry said the vessel likely tried to communicate via satellite yesterday.
The development happened as an international search mission was under way in the south Atlantic.
The ministry said seven failed "satellite calls" that it believes came from the ARA San Juan submarine were detected in a likely sign the crew was trying to reestablish contact.
The signals, in the late morning and early afternoon, lasted between four and 36 seconds, the ministry said.
Argentina is working on tracing the location with an unnamed US company specialised in satellite communications, the ministry said.
The satellite communications were believed to have failed because of foul weather, a source in the defense 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.
Whipping winds and more than 20-foot waves in the south Atlantic hindered the international search for the submarine.
The last confirmed location of the German-built ARA San Juan was 432km off Argentina's southern Atlantic coast early on Wednesday.
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.
As nations from Chile to South Africa offered help, Argentine sea vessels and planes scoured the southern sea.
But a storm pitching powerful winds and waves more than 20ft high has disrupted visibility and movement in the area, navy spokesman Enrique Balbi said.
The submarine's colour and design, which aim to camouflage the vessel in the ocean's surface, also posed a challenge.
"The idea is to continue through the night and the early morning, depending on weather conditions," Mr Balbi told reporters. The weather was expected to be somewhat improved today, he said.
A search of 80% of the area initially targeted for the operation turned up no sign of the vessel, but the crew should have ample supplies of food and oxygen, Mr Balbi added.
The dramatic search has captivated the nation of 44 million.
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 honor of the crew members.
Many relatives of the crew members awaited news at the city's naval base.
"We're hopeful this will end soon to remain only as a bad memory," a mother of one of the submarine crew members’ told journalists.