Scores of divers plunged into the Java Sea on Thursday to search the wreckage of flight QZ8501, which disappeared from radar screens on December 28, less than half-way into a two-hour flight from Indonesia's second-biggest city of Surabaya to Singapore.

After announcing the discovery of the plane's tail on Wednesday, officials have warned that weather conditions are likely to worsen from Friday onwards.

Choppy seas and poor visibility have dogged the search throughout. "The operation using a balloon or crane to lift the tail will start tomorrow," search and rescue agency coordinator Suryadi Supriyadi told reporters in Pangkalan Bun, the southern Borneo town closest to the crash site.

Black boxes believed to be in the plane's tail

The flight data and cockpit voice recorders could be crucial for determining what caused the jet carrying 162 passengers and crew to vanish. Four bodies recovered on Thursday raised the total to 44.

Officials are hopeful many of the bodies not yet recovered are inside the fuselage, which is thought to be lying near the plane's tail. Relatives of the victims have urged authorities to make finding the remains of their loved ones the main priority.

Days after sonar detected apparent wreckage, an unnamed underwater vehicle showed the upturned tail on the sea bed, about 30 kilometers (18 miles) from the plane's last known location.

Ping-emitting beacons in the black boxes still have about 20 days of battery life. Based on pictures taken by divers, investigators believe that the black boxes are still in their original location in the plane's tail.

"Once detected, we will try to find and lift up the black boxes as soon as possible," said Nurcahyo Utomo, an investigator from Indonesia's National Commission for Transportation Safety.

It's still not clear what caused the crash, but bad weather is believed to have been a factor. The pilot told air traffic control he was approaching threatening clouds. However, he was not given permission to change altitude because other planes were nearby.

jil/jr (Reuters, AP)