There has been no contact with the ARA San Juan since early on Wednesday, prompting Buenos Aires to launch an air and sea search with help from countries including Brazil, the United Kingdom, Chile, Uruguay and the United States.

 

The search has, however, been complicated by stormy conditions, Argentine navy spokesman Enrique Balbi said on Saturday.

 

However, the defense ministry said it had detected seven satellite-transmitted signals that may be an attempt by the submarine to resume contact.

 

The signals were received at 10:52 am (1352 GMT) and 3:42 pm (1842 GMT) on various naval bases with the help from US satellite communication experts, but they did not lock in, thus preventing a full connection.

 

"Right now, we are working to pinpoint the exact location of what is emitting the signals," presuming that it could be the missing sub, the ministry said.

 

Early Sunday, the US Southern Command said it was sending a second Navy P-8A Poseidon aircraft to join the search. The Florida-based plane and a crew of 21 are to reach Argentina later in the day.

 

A NASA P-3 research aircraft is already participating in the search, Southern Command said.

 

The California-based Undersea Rescue Command earlier said it was deploying two underwater crafts designed to rescue trapped submarine sailors at different depths, as well as a remotely-operated underwater robot known as an ROV.

 

"We will do what is necessary to find the submarine as soon as possible," Argentine President Mauricio Macri wrote on Twitter.

 

All land communications bases along the coast were ordered to scan for any followup, as family members of the missing waited nervously in the coastal city of Mar del Plata.

 

Claudio Rodriguez, whose brother Hernan is aboard the submarine, was hopeful, saying the satellite signals suggested the vessel was still afloat and would be found.

 

"They've got to be afloat. Thank God," he said.

 

"That gives us hope, because we knew that if they were down below, they would be screwed," he told TN news from the western city of Mendoza.