Hopes of finding the missing Argentinian submarine were dashed on Monday night as the navy said unusual noises picked up on sonar did not come from the vessel.

Search teams had been combing a 35 square nautical mile stretch of water 330 miles off the coast for the ARA San Juan after noises, thought to be the crew tapping on the hull of the vessel, were picked up by two search boats.

But the search is back on again after the sounds turned out to be bogus - the second time in 24 hours that rescue efforts had been scuppered.

Earlier in the day Navy spokesman Enrique Balbi said signals received over the weekend that were thought to be distress calls from the sub had come from somewhere else.

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

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

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

An international search operation is underway for the submarine, with the British Royal Navy deploying ice patrol ship HSM Protector to help

Mr Babli also warned that there could be just 48 hours to find the San Juan before the crew run out of oxygen.

Spokesman Enrique 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 five days, and search areas indicate it is likely in deep water, meaning sending up a snorkel would be problematic.

Mr Balbi said analysis of radio transmission received over the weekend revealed that they did not come from the sub. 'We have still been unable to contact [the crew],' he added.

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

One of the missing crew is 35-year-old weapons officer Eliana Krawczyk, who is the country's first female submariner.

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

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

More than a dozen boats and aircraft from Argentina, the United States, Britain, Chile and Brazil had joined the search effort.

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.

NASA has also sent its Lockheed P-3 Orion surveillance aircraft to the scene

A GPS map from November 18 shows the initial areas searched by NASA's aircraft. These include a small area off the coast of Comodoro Rivadavia, and a much larger area further north

A magnified version of the map shows the aircraft made several passes over the stretch of water before abandoning its efforts

Another map taken on Sunday shows the aircraft returned to another area slightly further south and made multiple passes over the water

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

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 Lockheed P-3 Orion 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'.

Relatives of the crew members gathered at the Mar del Plata Naval Base in the hopes of hearing news about their loved ones.

'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, weapons officer Ms Krawczyk,the only woman on board the German-built submarine.

From the Vatican, Argentine Pope Francis said he was making 'fervent prayers' for the crew.

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

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

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.

The navy believes the submarine, which left Ushuaia en route to the coastal city of Mar del Plata in Buenos Aires province, had communication difficulties that may have been caused by an electrical outage, Balbi said.

Navy protocol would call for the submarine to come to the surface once communication was lost.

He said: 'We expect that it is on the surface.'

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.