An Argentinian military submarine with 44 crew members on board has gone missing at sea.
Ships and aircraft have been scrambled to search for the vessel - named ARA San Juan - in the southern Argentine Sea.
It has been two days since the submarine provided its last location and navy spokesman Enrique Balbi said it may be suffering from a communications error.
"We are investigating the reasons for the lack of communication,” he said. “If there was a communication problem, the boat would have to come to the surface."
Mr Balbi said the submarine, which left the southern city of Ushuaia for Mar del Plata, more than 1,800 miles away, has food supply for several days and is likely to continue its journey despite the problem.
According to national Argentinian newspaper La Nacion, the 66-metre long, diesel-electric vessel was subjected to complex repair and engineering work in 2008, which the country's navy believed would extend its life by 30 years.
It was built in Germany in 1985 and arrived in Argentina a year later.