Search for missing Argentine submarine intensifies as the crew said to run out of oxygen today

US Navy aircraft reportedly detected a 'heat stain from a metallic object' at a depth of about 230ft

Separately, a rescue vessel allegedly reported hearing an infrasound sonar signal late Tuesday night

Sub with 44 crew went missing last Wednesday while sailing from Ushuaia to naval base in Mar del Plata

They sailed on Monday, communication was lost on Wednesday, and search is now involving several nations

An Argentine Navy spokesman warned yesterday that the crew only have oxygen until Wednesday morning

The missing Argentine submarine may have been located early this morning, after a US Navy aircraft allegedly detected a 'heat stain' from 230ft below the surface, some 185miles from the coast, and a rescue vessel separately reported hearing a sonar signal.

The ARA San Juan was sailing from Ushuaia to Mar del Plata when it disappeared with 44 crew members last Wednesday, including Argentina's first female submariner Eliana Krawczyk, 35, and Luis Niz, 25, who is due to get married in two weeks time.

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The crew's oxygen supply was due to run out this morning as they only had enough on board to last seven days - leaving the international rescue mission racing against time to the spot where the signals were detected.

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Rescue mission: Argentina's Navy destroyer ARA Sarandi sails off to take part in the search of missing submarine ARA San Juan, from the north breakwater of Argentina's Navy base in Mar del Plata, on the Atlantic coast south of Buenos Aires

The ARA San Juan (pictured) has been missing for a week after reporting a fault before dropping out of communications

The ARA San Juan would have enough oxygen for its crew to survive underwater for seven days, if there was no hull breach, according to officials, a time which would have elapsed at 7.30am GMT.

'We are in the critical phase...particularly with respect to oxygen,' navy spokesman Enrique Balbi said Wednesday. 'There has been no contact with anything that could be the San Juan submarine.'

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Experts, however, have said it was possible that the diesel-electric submarine's oxygen supply might last as many as ten days in the case of a battery failure as reported by the boat's captain in his last communication.

Capt. Balbi, added: 'The seven days is not dogmatic. It varies according to the circumstances. As a submariner, I am not losing hope.'

Argentine news report that two separate clues to ARA San Juan's location have been detected.

A US Navy airplane is said to have recorded 'a 'heat stain', which would correspond to a metal object', some 186miles off the coast of Puerto Madryn, which could be the ARA San Juan,Clarin.com reports.

The other is a so-called infrasound signal picked up by one of the rescue ships using sonar, the website added.

A woman looks at signs in support of the 44 crew members of the ARA San Juan submarine missing at sea, which are placed on a fence outside the Argentine Naval Base where the submarine sailed from

Waiting game: Maria Rosa Belenstro, right, mother of missing submariner Fernando Villareal, is comforted by a local woman outside Argentina's Navy base in Mar del Plata

Waiting: Friends and family wait outside the Naval base in Mar del Plata to hear of news of the missing submarine

BRITAINS ITS HELP: SHIPS, PARACHUTE TEAMS AND USE OF FALKLANDS AIRFIELD The Royal Navy has assisted the search in a number of ways. These include the HSM Protector polar exploration vessel, and the HMS Clyde. An RAF Voyager aircraft is expected to arrive in Argentina on Wednesday, carrying three tons of tonnes of equipment, including 12 deep emergency life support stores pods. The Royal Navy Submarine Parachute Assistance Group (SPAG) arrived at Mount Pleasant Airfield, in the Falklands yesterday. The rapid deployment team is designed to provide quick response to submarines in peril. An RAF C-130 aircraft based in the Falkland Islands also joined the search on Sunday, as well as an RAF Voyager Air to Air Refuelling aircraft. In addition, three UK Liaison Officers have been deployed to the Argentinian Navy Headquarters coordinating the search and rescue operation. The UK has also offered the use of Mount Pleasant Airfield, but no country has yet taken up the offer.

Hopes were buoyed earlier this week, after brief satellite calls were received and when sounds were detected deep in the South Atlantic. But experts later determined that neither was from the missing sub.

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A U.S. Navy P-8 Poseidon aircraft spotted white flares, but the Argentine navy said they were unlikely to be from the San Juan, which carried red and green flares. The navy said a life raft that was found in the search area early Tuesday didn't belong to the submarine and likely fell off another vessel.

Families have gathered at the Naval Base in Mar del Plata as they anxiously await news of their loved ones, who have now been missing for a week.

'We feel anguish. We are reserved but will not lose our hope that they will return,' Marcela Moyano, wife of machinist Hernan Rodriguez, told television network TN.

'We're very worried, we have little news, we're waiting for communication,' said Eduardo Krawczyk, father of weapons officer Ms Krawczyk.

'We can make up a thousand movies with happy and sad endings, but the reality is that the days pass by and not knowing anything kills you,' Carlos Mendoza, the brother of submarine officer Fernando Ariel Mendoza said.

'Every minute is oxygen that's worth gold.'

Many are also taking to social media to express their worries as the search continued into a second week, including Sofi Álvarez, 21, whose brother Luis Niz, 25, is on the ARA San Juan.

She tweeted: 'We are here, all united, awaiting your arrival, 44 families and a very long wait. Do not stop asking, please, do not lose faith, hope. We are not going to stop until we hug them again.'

'It does not matter what god you believe in, or what you believe, I only ask that with a prayer, good vibes, good energies ask for the alive appearance of the crew of the Argentine submarine ARA San Juan, one of them my eldest brother. I'm destroyed.'

Juan Carlos Mendoza, father of Fernando Mendoza, a crew member of the missing submarine ARA San Juan, stands outside the Navel base in Mar del Plata

People look at an Argentine flag carrying the Spanish message: "Strength. We trust. We wait." on a fence at the Naval base

Hope: A family looks at Argentine Navy destroyer ARA Sarandi docked at Argentina's Navy base in Mar del Plata, on the Atlantic coast south of Buenos Aires

'I AM CONVINCED THEY WILL BE OK': WIFE OF MISSING CREW MEMBER HAS HOPE By GERARD COUZENS For MAILONLINE The wife of one of the 44 crew members on board missing Argentinian submarine ARA San Juan has said the rescue of 33 trapped Chilean miners seven years ago is helping her stay optimistic. First Lieutenant Fernando Ariel Mendoza's relatives are among those who have gathered at a naval base in the Atlantic resort city of Mar del Plata as they anxiously await news of their loved ones. His sister-in-law Marcela Tagliafeta told Argentinian daily Clarin today the survival of the miners - trapped 2,300 feet underground for 69 days after a cave-in in August 2010 - was keeping her hopes of a family reunion alive. She said: 'I am convinced that if the 33 Chilean miners survived, our 44 are aso going to come out okay. 'They are 44 good people who don't deserve an unhappy ending.' Marcela spoke as Fernando's fisherman brother Carlos hung an Argentinian flag on a perimeter fence at the naval base, with the inked handprints of the missing submarine officer's two children Fernando and Magali on it alongside the message: 'Stay strong daddy.' His wife Carolina stayed at home and made sure the youngsters were kept away from TV news about the ongoing operation to locate the submarine. The San Jose copper-gold mine accident in the Atacama Desert, 28 miles north of the regional capital of Copiapo, began on August 5 2010. The 33 men trapped by a rock the size of the Empire State building were cut off completely from the world for 17 days until rescuers were able to drill down to the tunnel where they were sheltering to find they had survived. Their dramatic experience, including their rescue nearly two months later, was later turned into a Hollywood film called 'The 33' starring Antonio Banderas.

THE SEARCH FOR ARA SAN JUAN Friday 10/11: The submarine leaves Mar del Plata for Ushuaia for a routine exercise mission. Monday 13/11: ARA San Juan sets off from Ushuaia to return to the Mar del Plata Naval Base. At some point before this, Eliana Krawczyk calls her family. Wednesday 15/11: The crew's last known communications with the Navy. Two calls are made, 267 miles off the coast, in the Gulf of San Jorge, one of which reports a routine battery fault. Thursday 16/11: The Argentine Navy launches a search mission after over one day of silence from the vessel. Friday 17/11: The US Navy and NASA deploy surveillance air crafts to help. Saturday 18/11: Argentina's Ministry of Defence reports that failed attempts at satellite calls had been made from the submarine, but these were later found to come from a different source. British military also join the search. Monday 20/11: Sounds are detected by probes deep in the South Atlantic and are thought to be crew members banging on the hull. This is later determined to be 'biological' sounds, and not from the submarine. It is revealed the vessel only has enough oxygen for seven days below the surface.

Speaking to MailOnline, she added: 'We always talk to him before he leaves port and he did not give us any indication of a breakdown, on the contrary, he told me that in a few days we would see each other.

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'He is about to get married in a few weeks.'

From the Vatican, Argentine Pope Francis said he was making 'fervent prayers' for the crew, and prayers have also come from legendary footballer Diego Maradona.

'I want to send strength and hope to all the relatives of the crew of the ARA San Juan submarine,' Maradona wrote on his official Instagram account.

'I think it's great that we are receiving help from other countries with better technology. And, although I wonder about those responsible for this situation, I think that today the most important thing is to rescue our boys.'

This comes after one of the crew members reportedly warned her family that there had been issues on board, just days before it vanished.

Ms Krawczyk's brother has since revealed that she called the family before they set off and told them there was a mechanical problem.

Speaking to Argentine radio and newspapers, Roberto Krawczyk has said his sister told him that the submarine had needed repairs while in port.

ARA San Juan was returning to its base in Mar del Plata after a routine mission, and left Ushuaia last Monday. Authorities lost contact with the vessel two days later.

Navy spokesman Balbi said that if the sub was settled on the surface, or able to put up a snorkel to draw fresh air, there are supplies on board to last for a month.

But if the sub is underwater - as seems to be the case after surface searches failed to find it - then there is only enough air inside to last for a week.

The craft has already been missing for seven days, and search areas indicate it is likely in deep water, meaning sending up a snorkel would be problematic.

One of the 44 missing crew members is weapons officer Eliana Krawczyk, 35, Argentina's first female submariner

Eliana Krawczyk, 35, had spoken to her brother while in port in Ushuaia, and told him that there had been an mechanical issue on board the ARA San Juan

Krawczyk, 35, is one of the crew on board the vessel which went missing last week

'F*** you, pirates!': Argentine politicians attack British Navy for helping with search for ARA San Juan Aggressive: Argentina's Workers' Party leader Gabriel Solano Two leading Argentine politicians have come under fire after branding British Navy forces that have joined the search for the lost ARA San Juan submarine as 'pirates'. Britain's HMS Protector has been scouring the South Atlantic as part of the international hunt for the missing vessel, and is being joined by HMS Clyde which has been diverted from South Georgia. The Royal Navy has also deployed its elite submarine rescue team to join the search. The highly trained team of medics, engineers and escape specialists is continuously on six hours notice to go anywhere in the world. But despite the increasing desperation to find the crew alive, Argentina's Workers' Party leader Gabriel Solano yesterday appeared to prefer that British forces did not help in the search, instead tweeting: 'F*** you! pirates.' He then added: 'You are responsible for war crimes, like the sinking of the General Belgrano.' The opposition party leader and Argentine legislator had earlier commented on a tweet from the British embassy in Buenos Aires that British forces were joining in the search, writing: 'You are occupying troops in Argentine territories'. He was immediately attacked by ordinary Argentinians who branded him an '***hole' and a 'moron'. His comments come after another politician, Fernando Esteche, leader of the Quebracho party, also used Twitter to attack the deployment of British forces in the search for the missing sub. He replied to a post about the operation on the Falkland Islands Twitter account: PIRATES NOW AND ALWAYS!!!!' He later wrote: 'Yesterday they sank the Belgrano outside the exclusion zone and today they want thanks for their collaboration in the search for the ARA San Juan. That they help but that they do not expect anything in return because they still occupy our islands. These are the laws of the sea!' Agai, he was criticised by Argentinians growing increasingly concerned about the fate of the 44 submarine crew members.

The last known communications from the sub's crew were on Wednesday last week. One call reported a routine battery fault, while the details of the second call have not been disclosed by the navy.

A multinational air and sea search is under way with help from countries including Brazil, Britain, Chile, the United States and Uruguay.

Storms, seen in this video, have complicated efforts to find the navy submarine, which had gone missing in the South Atlantic.

Authorities have mainly been scanning the sea from above, as storms have made the search difficult for boats.

The Royal Navy has deployed an ice patrol ship to help search for the missing submarine.

Britain sent the HSM Protector, a polar exploration vessel, to the southern Argentine Sea to assist in searches.

Britain and Argentina fought a war in 1982 over the Falklands Islands, which are called the Malvinas in Argentina.

Working together: This graphic shows the vessels and aircrafts as well as their country of origin involved in the search

The missing submarine was sailing from Ushuaia to Mar Del Plata when it vanished

Support: Legendary footballer Diego Maradona has posted this message of support, translated from Spanish

President Mauricio Macri met with vice admiral Miguel Angel Mascolo (right) rear admiral Gabriel Gonalez (center) as search efforts continued on Monday night

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A spokesman for the British Navy said: 'Following a request from the Argentine government, HMS Protector has been deployed to join the search and rescue effort for the ARA San Juan.'

The US Navy ordered its Undersea Rescue Command based in San Diego, California, to deploy to Argentina to support the search for the submarine.

NASA also sent its Antarctic P-3 Poseidon surveillance aircraft.

President Mauricio Macri said in a tweet that the country will use 'all resources national and international that are necessary to find the submarine'.

The TR-1700 class diesel electric submarine had been returning from a routine mission to Ushuaia near the southernmost tip of South America, to its base at Mar del Plata, around 240 miles south of Buenos Aires.

The San Juan is one of three submarines in the Argentine fleet.

The 213-foot long submarine was built in 1983 by Germany's Thyssen Nordseewerke. However, it underwent a seven-year refit between 2007 and 2014 to extend its life by a further 30 years.

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The German-built submarine, which uses diesel-electric propulsion, was inaugurated in 1983, making it the newest of the three submarines in the navy's fleet, according to the navy.