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.
Flight tracking website FlightRadar24 showed the jet sharply dropped from an altitude of 29,100 to 7,850 feet (about 8,900 to 2,400 metres) in just over a minute.
After a brief upswing, it dropped again to 3,225 feet, the tracker said.
On Wednesday, rescuers were forced to pause the search as rains raised risks to teams working in a zone where a large pit has been bored out by the impact of the aircraft.
A reporter for state broadcaster CCTV given access to the crash area said there were risks of "small-scale landslides" as rain had destabilised the steep slopes.
President Xi Jinping was swift to order a probe into the crash, dispatching senior Communist Party officials to the scene, including close aide Vice Premier Liu He.
The Civil Aviation Administration of China has said it will conduct a two-week safety inspection across the industry.
Authorities have sealed off access to the crash site and blocked foreign media from speaking to the distraught relatives who have gathered in Wuzhou.
China Eastern said the crashed plane, which was nearly seven years old, had met all airworthiness requirements pre-flight.
Aviation authorities said more painstaking evidence gathering was needed before coming to any conclusions.