This undated photo provided by the Argentina Navy shows an ARA San Juan, a German-built diesel-electric vessel, near Buenos Aires, Argentina. Argentina’s Navy said Friday, Nov. 17, 2017, it has lost contact with its ARA San Juan submarine off the country’s southern coast. (Argentina Navy via AP )

On Wednesday, the Argentine Navy lost contact with one of its submarines.

The ARA San Juan is a diesel-electric attack built in Emden, Germany in 1982. It had been on a routine patrol from the Ushuaia naval base to the Mar del Plata base. Several nations are now involved in search operations. The US contribution, a P-8A Poseidon maritime patrol aircraft remained the best hope of finding that ship and its 44 crew members, and seven short satellite phone pulses from the ARA San Juan on Saturday give hope that a rescue may be effected.

If the San Juan can be found and some or all of the crew are still alive, there is a very good chance that a rescue can be made. Both UK and US submarine rescue assets have been put on alert.