The Argentine Navy has confirmed the deaths of all 44 crew members of the submarine ARA San Juan citing explosion on-board as the cause of the accident.
"An anomalous, singular, short, violent and non-nuclear event consistent with an explosion," occurred shortly after the submarine's last communication, navy spokesman Captain Enrique Balbi told a news conference in Buenos Aires, according to AFP reports Friday.
Underwater sounds detected in the first days of the search by two Argentine search ships were determined to originate from a sea creature, not the vessel. Satellite signals were also determined to be false alarms.
The San Juan, a 34-year-old German-built diesel-electric submarine, had reported a battery problem on November 15 and said it was diverting to Mar del Plata, but did not send a distress signal, according to the navy.
Balbi admitted on Wednesday that the situation for the sub and its crew appeared to be worsening. However, he refused to speculate at that point on the origin of what he initially described as a "hydro-acoustic anomaly" detected in the ocean almost three hours after the sub's communication and 30 miles (50 kilometers) north of its last known position.
Balbi explained that information about the unusual noise only became available Wednesday after being relayed by the United States and "after all the information from all agencies reporting such hydro-acoustic events was reviewed".
Explaining the lack of debris on the surface, Balbi said "nothing will end up floating to the surface" because a submarine "implodes".
Gustavo Mauvecin, director of the Center for Hyperbaric Medicine at Mar del Plata, said hydrogen "is always an issue with submarines with electric engines".
The San Juan "has 500 tons of lead-acid batteries, which release hydrogen if there is an overcharge in the battery, hydrogen in contact with oxygen is explosive".