No sign of the vessel has been reported since November 15, shortly after the captain reported an electrical fault.
The missing Argentine submarine San Juan was carrying more than three times the amount of people allowed, declared the brother of a crew member to local media on Sunday.
The ship was only suited for 37 permanent spots but was instead carrying 44 people on board, he said to RIA Novosti.
Moreover, the seven extra people had no expertise in submarine navigation. Among them were two combat swimmers from Argentine Navy's Buzos Tácticos and an official from the Navy Intelligence Service, whose wife leaked the information.
The day before, the relatives of the 44 missing crew members held a religious ceremony, even though the Navy has yet to declare them dead.
But many relatives of the crew have lost hope since the Navy announced Thursday that there had been an explosion on board the submarine, which experts said was likely linked to a problem with its batteries and would likely have been catastrophic.
President Mauricio Macri on Friday ordered an inquiry to "know the truth" about what happened to the San Juan.
Argentina's navy has been fiercely criticized for its handling of the operation since first reporting on November 16 that the San Juan had not returned to base as scheduled.
Opposition politicians blamed the loss on a reduction in funding for the armed forces, whose budget has declined since the fall of a military dictatorship in the 1980s.
Magistrate Marta Yanez has already begun preliminary investigations into the disaster.
She told reporters that unlike a plane, "the submarine does not have a black box. The black box is the submarine," and it would have to be recovered before the causes of the explosion could be known.
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