The US Navy has deployed unmanned underwater vehicles (UUV) to search for the Argentine navy's submarine, ARA San Juan, in south Atlantic waters.
The Bluefin 12D (Deep) UUV and three Iver 580 UUVs operated by the Hawaiian-based US Navy's Unmanned Undersea Vehicle Squadron 1.
The UUVs can search wide areas of the ocean using side scan sonar, a system that is used to efficiently create an image of large areas of the sea floor.
The Bluefin 12D can conduct search operations at three knots at a maximum depth of 1,500 metres for 30 hours.
The Iver 580s can operate at a depth of 99 metres, travelling at 2.5 knots for up to 14 hours.
The US government is providing rapid-response capabilities, including aircraft, equipment and personnel to assist.