Seven signals picked up at the weekend were not from a missing submarine’s satellite phone, Argentina’s navy says.
The failed calls, lasting between four and 36 seconds, had been received on Saturday.
They had raised hopes that the 44 crew members of the boat, the ARA San Juan, were alive.
The submarine disappeared 430km (267 miles) off the Argentine coast on Wednesday and no traces of it have been located.
US satellite company Iridium had earlier said that the submarine carried one of its satellite phones on board.
But the company said that the seven signals detected on Saturday did not come through its network.
On Monday, navy spokesman Enrique Balbi confirmed that “the seven attempted calls did not come from the submarine’s satellite phone”.
A huge search and rescue operation is continuing in the South Atlantic, where the vessel disappeared five days ago.
Specialist underwater rescue equipment has arrived in Argentina from the United States and more boats and planes have also joined the search, which has been hampered by heavy winds and high waves.
Vanished on the way home
The ARA San Juan was returning from a routine mission to Ushuaia, near the southern-most tip of South America, to its base at Mar del Plata, south of Buenos Aires.
Its last contact with navy command was on Wednesday morning.
It is thought that the submarine may have had communication difficulties caused by a power cut.
Navy protocol dictates that a vessel should come to the surface if communication has been lost.