Search crews have recovered 30 bodies from the AirAsia plane crash, and an Indonesian navy official says five were found still strapped in their seats.

Colonel Yayan Sofiyan, commander of the warship Bung Tomo, told MetroTV that the five were among seven bodies retrieved from the Java Sea and taken to an Indonesian vessel today.

Indonesian search and rescue chief Henry Bambang Soelistyo later said a total of 30 bodies had been recovered from Flight 8501.

There were 162 passengers and crew on the plane that went down on Sunday, half-way through a flight from Indonesia to Singapore.

The investigation into the crash has turned to the sea floor, with more sonar equipment and metal detectors deployed to scour the seabed for wreckage, including the plane's black boxes.

Rescuers hope the fuselage - if intact - will contain the remains of many of those still missing. The wreckage will be key to explaining what might have caused Flight 8501 to go down.

The Airbus A320 crashed in to the Java Sea on Sunday on a flight from Surabaya, Indonesia's second-largest city, to Singapore. Minutes earlier, the pilot had told air traffic control he was approaching threatening clouds, but was denied permission to climb to a higher altitude because of heavy air traffic.

More ships arrived today with sensitive equipment to hunt for the plane's fuselage.

"We will focus on underwater detection," said Mr Soelistyo. He added that ships from Indonesia, Malaysia, Singapore and the US had been on the scene since before dawn to try to pinpoint wreckage and the all-important flight data and cockpit voice recorders.

The data recorder contains crucial information such as engine temperature, vertical and horizontal speed and hundreds of other measurements. The voice recorder captures conversations between pilots and other sounds from the cockpit.

Mr Soelistyo said bad weather, which has hindered the search for the past few days, remained a worry. A drizzle and light clouds covered the area today, but rain, strong winds and high waves up to 13ft were forecast until Sunday. Strong sea currents have also kept debris moving.

Nine planes, many with metal detecting equipment, were also scouring a 8,380 square mile area off Pangkalan Bun. Two Japanese ships with three helicopters were on their way, Mr Soelistyo said.

He estimated the fuselage was at a depth of about 80ft to 100ft.