Search teams scouring the South Atlantic for a missing Argentinian submarine say sonar "noise" detected in the ocean's depths did not come from the vessel, which has only one day's worth of oxygen left.
- New signals were picked up on sonar but turned out to be a false alarm
- The sub suffered an electrical fault just before losing contact
- The Navy now says satellite calls picked up on Saturday were not from the San Juan
Hopes of finding the ARA San Juan, which went missing last Wednesday with 44 crew on board, are waning.
Two possible leads have now been discounted.
The navy said satellite calls detected over the weekend did not in fact come from the vessel.
And this morning officials also confirmed sonar "noise" detected by probes deep in the South Atlantic was not linked to the San Juan.
There had been speculation the "constant" noises could have been caused by sailors banging on the boat's hull to attract attention.
Sub had surfaced to call in an electrical fault
Overnight the navy confirmed the submarine had reported an electrical problem and was headed back to base just before it disappeared 432 kilometres off the coast.
"The submarine surfaced and reported a malfunction, which is why its ground command ordered it to return to its naval base at Mar del Plata," Commander Galeazzi said.
Navy spokesman Enrique Balbi said the craft was carrying enough oxygen to spend seven days underwater.
After that, he said, it would have to surface or get near the surface to replenish air supply.
Intermittent satellite communications had been detected on Saturday and the navy had said they were likely to have come from the submarine. But that has since been ruled out.
More than a dozen ships and aircraft from Argentina, the United States, Britain, Chile and Brazil have now joined the hunt for the San Juan, but storms have complicated efforts to find the vessel.
Commander Galeazzi said it was normal for submarines to suffer system malfunctions.
"A warship has a lot of backup systems, to allow it to move from one to another when there is a breakdown," he said.
Anxious relatives wait for news
Crew members' relatives gathered at the Mar del Plata naval base waiting for news.
They were joined by President Mauricio Macri, who arrived late in the morning but did not address the media.
"There is no good news," said Juan Carlos Mendoza, father of crew member Fernando Mendoza.
"Hopefully they have oxygen."
The ARA San Juan was inaugurated in 1983, making it the newest of the three submarines in the navy's fleet.
Built in Germany, it underwent maintenance in 2008 in Argentina.
That maintenance included the replacement of its four diesel engines and its electric propeller engines, according to specialist publication Jane's Sentinel.