The US Navy has picked up signals from the flight data recorders, or black boxes, of an Indonesian jetliner that crashed into the sea on New Year's Day with 102 people onboard, the US Embassy said on January 25.

The US Mary Sears located signals "on the same frequency of the black boxes associated with the missing airplane", a statement issued by the embassy in Jakarta said.

Data from the flight recorders will be crucial in determining the cause of the crash, but retrieving them from the ocean floor at a depth of some 1,700 meters will likely be a difficult, expensive and lengthy operation.