Parts of the Boeing 737-800 were strewn across mountain slopes charred by fire after China's first crash involving a commercial jetliner since 2010.
Burnt remains of identity cards and wallets were also seen, state media reported.
Flight MU5735 was en route from Kunming, capital of the southwestern province of Yunnan, to the port city of Guangzhou when it suddenly plunged from cruising altitude at about the time when it would normally start to descend ahead of its landing.
Chinese media carried brief highway video footage from a vehicle's dashcam apparently showing a jet diving to the ground at an angle of about 35 degrees off vertical.
Si, 64, a villager near the crash site who declined to provide his first name, told Reuters he heard a "bang, bang" at the time of the crash.
"It was like thunder!" he said.
State media have described the situation as "grim", and that the possibility of all onboard perishing could not be ruled out.
The crash site was hemmed in by mountains on three sides, according to state media reports, with access provided by just one tiny path. Rain was forecast in the area this week.
Excavators were clearing a path to the crash site on Tuesday, state television showed.
Earlier, video footage from People's Daily showed search and rescue workers and paramilitary forces scaling tree-covered hillocks and placing markers wherever debris was found.
Police set up a checkpoint at Lu village, on the approach to the site, and barred journalists from entering.
US-based aviation analyst Robert Mann of R.W. Mann & Company said investigators will need the flight data recorders to understand what might have caused the abrupt descent suggested by Automatic Dependent Surveillance-Broadcast (ADS-B) data. ADS-B is a technology that allows aircraft to be tracked.
The crash comes as Boeing seeks to rebound from several overlapping crises, including the coronavirus pandemic and crashes involving its 737 MAX model.
"Accidents that start at cruise altitude are usually caused by weather, deliberate sabotage, or pilot error," Dan Elwell, a former Federal Aviation Administration head, told Reuters.
Elwell, who led the FAA during the 737-MAX crisis, said mechanical failures in modern commercial jets were rare at cruise altitude.
China Eastern and two of its subsidiaries on Monday grounded its fleet of 737-800 planes. The group has 225 of the aircraft, data from British aviation consultancy IBA shows.
Other Chinese airlines have yet to cancel any of their flights that use 737-800 aircraft.
A provincial daily cited a woman as saying six of her family members and friends were on the flight to Guangzhou, where they had been due to attend a funeral.
The last crash of a commercial jetliner in China was in 2010, when an Embraer E-190 regional jet flown by Henan Airlines crashed in northeast China, killing 44 of 96 people on board.
