The plane went down early Monday just minutes after takeoff from Beirut in a fierce storm. All 90 people on board were feared dead.
It could take days to retrieve the plane's flight recorders, which were located late Wednesday. The Lebanese army said in a statement that the USS Ramage and a civilian ship from Cyprus were scanning the area.
Walid Noshie, a prominent Lebanese diver who is helping the search, said the priority is to find the people on the plane, and then the black boxes.
Noshie said crews were using sophisticated equipment, including an underwater torpedo to scan the water and sonar-equipped cables that stretch almost 2 miles (3 kilometers).
He said the black boxes might not be retrieved until Friday or later.
Rescue teams have recovered some bodies and pieces of the plane, but hope for finding any survivors has faded. There are conflicting numbers of how many bodies have been found, although at least a dozen have been pulled out of the chilly waters of the Mediterranean Sea.
The flight recorders are critical to determining what caused the crash. Lebanon's transportation minister has said the plane made a "fast and strange turn" after takeoff, and weather experts said lightning struck in the flight path around the time of the crash.
The Lebanese army and witnesses reported the plane was in flames as it went down.
Health officials have handed over to families the remains of four victims who were identified using DNA, including a 2-year-old girl, Health Minister Mohammed Jawad Khalife said.
Searchers have fanned out for 18 miles (30 kilometers) along Beirut's coast, and about 5 miles (8 kilometers) out to sea, according to a Lebanese army official.