A black box from the crashed China Eastern airliner was recovered on Wednesday as investigators try to piece together what made a jet carrying 132 passengers nosedive into a mountainside in southern China.

The cause of the disaster has mystified aviation authorities who have scoured rugged terrain for clues, finding no survivors from what is almost certain to be China’s deadliest plane crash in nearly 30 years.

A flight recorder “from China Eastern MU5735 was found,” on Wednesday Liu Lusong, a spokesman for China’s aviation authority, told reporters, although state media later said it was badly damaged.

The Boeing 737-800 is equipped with two flight recorders: one in the rear passenger cabin tracking flight data, and the other a cockpit voice recorder.

“At present, it is unclear whether it is a data recorder or a cockpit voice recorder,” that has been found, Mao Yanfeng, an official at the Civil Aviation Administration of China (CAAC), said according to state media.

Officials have still refrained from declaring all of the passengers dead despite the pulverised mass of twisted metal and charred belongings that has greeted recovery teams on the mountainside.

On Wednesday afternoon AFP reporters saw a small crowd of people guided by officials across the police cordon that marks entry to the site, huddled under umbrellas in the driving rain.

One middle-aged man later confirmed that he was the relative of someone on the fight, and asked the media not to crowd around him.

The Boeing 737-800 plane went down near Wuzhou in southern China on Monday afternoon after losing contact with air traffic control. (AFP)