An Argentine submarine that went missing with at least 44 crew members on board in the South Atlantic has prompted the navy to intensify the search operation.

Naval spokesman Enrique Balbi said on Friday (17 November) that the ARA San Juan was in the southern Argentine sea 432km from the Patagonian coast on Wednesday morning when it last communicated. It was returning from a routine mission to Ushuaia near the southernmost tip of South America to its base at Mar del Plata, around 400km south of Buenos Aires, when it went missing.

However, when it failed to send signals for two consecutive days, the navy stepped up its search efforts in difficult weather conditions, Reuters reported.

Balbi said heavy winds and high waves in the region were making the search more complicated, and added that the emergency operation has been formally upgraded to a "search and rescue" on Friday evening after no visual or radar contact was made with the watercraft.

"Detection has been difficult despite the quantity of boats and aircraft [in in the search]. Obviously, the number of hours that have passed — two days in which there has been no communication — is of note," he told the media houses.

Naval spokesman had earlier speculated that the submarine might be facing an electrical issue. But the Navy's working hypothesis is that the submarine might be facing communication difficulties off the province of Chubut because of a possible electrical outage.

"We are investigating the reasons for the lack of communication. If there was a communication problem, the boat would have to come to the surface," Balbi said.

According to Argentina Navy, the German-built submarine is the newest addition to the three submarines in the navy's convoy. It was commissioned in 1985.

Meanwhile, media reports stated that the US, Britain and Chile have offered "logistic support and information exchange in this humanitarian search". The UK government has offered to assist, with an A C130 Hercules stationed in the Falklands Islands on standby if required, The Sky News reported.

On the other hand, America's NASA P-3 explorer aircraft, which had been stationed in the southern city of Ushuaia to depart to Antarctica, is also expected to fly over the search area. A Hercules C-130 from the Argentine Air Force will also be flying over the operational area.

President Mauricio Macri said the government is in constant contact with the crew's families. "We share their concern and that of all Argentines. We are committed to using all national and international resources necessary to find the ARA San Juan submarine as soon as possible," he tweeted.