MAR DEL PLATA: The search for the Argentine submarine missing in the south Atlantic shifted from rescue to recovery Friday, as navy officials lost hope of finding any of the 44 crew members alive.
"We have to find the submarine at the bottom of the sea, the area is large, the environment hostile, and the search very difficult," said Argentine navy spokeman Enrique Balbi.
On Thursday Balbi revealed that there had been an explosion onboard the San Juan shortly after the submarine signaled a problem with its batteries on November 15.
Officially the navy has not declared the loss of the crew, but marine experts believe an explosion would have been catastrophic.
Brenda Salva, friend of crew member Damian Tagliapietra, said she had been told by the commander of the Mar del Plata naval base: "They are all dead".
For the relatives of the crew, grief had turned to anger by Friday.
"I want to tell Admiral Marcelo Srur that he is not in a position to be in charge of a force, and to the president (Mauricio Macri), to bring order," said Maria Rosa Belcastro, mother of 38-year-old Lieutenant Fernando Villarreal.
Relatives have focused their anger on the condition of the 34-year-old sub, which had undergone a seven-year refit to extend its service, and the navy's guardedness since the start of the search operation.
Balbi responded to criticism by saying that "no ship would put to sea if it was unseaworthy".
- Heads to roll -
Argentine press reports on Friday said the center-right government of President Mauricio Macri was preparing to sack navy chief Srur in a purge of top brass in a country where the military is distrusted.
Memories are still fresh in Argentina of the 1976-83 military dictatorship responsible for the disappearance of an estimated 30,000 people.
The San Juan tragedy comes a month after Macri's government was accused of a cover-up in the killing of activist Santiago Maldonado after he was arrested by security forces during an indigenous rights protest.
"The government is considering changing the leadership of the navy. They believe there was negligence in the disappearance of the ARA San Juan and criticize the handling of the situation," the influential Clarin daily said.
One newspaper reported that the navy had taken five days to inform the defense ministry of a battery problem aboard the German-built diesel-electric submarine.
The explosion, detected just hours after the sub's last contact on November 15, is likely to have been associated with the battery problem it reported, experts say.
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," said Gustavo Mauvecin, director of the Center for Hyperbaric Medicine at Mar del Plata.
Horacio Tobias, a former diver aboard the San Juan, said the blast was likely "so violent that they did not have time to realize anything."
Depths plummet from 200 meters (650 feet) to over 3,000 meters on the edge of the Argentine shelf, where the sound of the explosion was picked up by hyrdo-acoustic sensors used by the Nuclear Test-Ban Treaty Organization.
Experts say the sub would begin to break-up once below depths of around 600 meters.
Argentina is leading an air-and-sea search to try to still find the sub. It is getting help from several countries now including Brazil, Britain, Chile, Colombia, France, Germany, Peru, Russia, the United States and Uruguay.
A Russian oceanographic research ship was steaming towards the area on Friday to join the operation, equipped with two mini-subs designed to work at depths of 6,000 meters.