A naval Argentine submarine is missing in the South Atlantic. Here is what we know:
The ARA San Juan submarine, with a crew of 44 people on board, has been missing since Wednesday, 15 November.
The vessel, 65 metres long and seven metres wide, was 432km off Argentina's coast when its location was last known.
It was returning from a routine mission to Ushuaia, near the southernmost tip of South America, to its base at Mar del Plata, which is about 400km south of Buenos Aires.
The vessel had reported an electrical problem and was headed back to its base in the port of Mar del Plata when it disappeared.
The submarine had come up from the depths and reported the unspecified electrical malfunction before it disappeared.
The craft was navigating normally, under water, at a speed of five knots towards Mar del Plata when it was last heard from.
Satellite calls detected over the weekend had been seen as hope that the crew were alive. However, a navy spokesman on Monday confirmed that the calls did not come from the vessel.
A sound detected yesterday, Monday, in the South Atlantic is also not believed to have come from the vessel.
Among those on board is Argentina's first female submarine officer, 35-year-old weapons officer Eliana Krawczyk.
An air and sea search is under way in bad weather conditions with help from Brazil, Britain, Chile, the US and Uruguay among others.
Rescuers are focusing on an ocean patch about 300km in diameter, radiating from the last point of contact.
The navy has not ruled out any hypothesis. A spokesman said the most likely scenario is that an electrical problem may have unexpectedly cut off the vessel's communications.
Protocol calls for submarines to surface if communication is lost.
The ARA San Juan was built in Germany and inaugurated in 1983, making it the newest of the three submarines in the navy's fleet.
It underwent a re-fit between 2007 and 2014 to extend its usefulness by some 30 years.
