Both flight recorders, or black boxes, of the China Eastern Airlines passenger plane that crashed in south China on March 21 are being decoded, an aviation official said Thursday.

Preliminary analysis is being carried out after the site environment, debris distribution and impact marks have been located and photographed, said Zhu Tao, head of the aviation safety office of the Civil Aviation Administration of China.

Aviation experts are also studying and judging the possible trajectory, posture and impact force of the aircraft when hitting the ground, Zhu told a press briefing.

"By analyzing the data of air traffic control's radar automation system, we're trying to restore the real flight process before the crash," he said, adding that information on the flight's passengers, luggage, cargo and mail are also being examined.