The pre-dawn landslide buried 18 homes and sparked the evacuation of more than 200 people when it struck in Zhenxiong County, Yunnan province early Monday.
More than 30 hours since the disaster, twenty people have been confirmed dead, state broadcaster CCTV said.
Twenty-four remain missing, the report added.
State news agency Xinhua said rescue workers are now in a "race against time" to find those still missing, after a night of sub-zero temperatures.
"Search and rescue efforts persisted through the night," firefighter Li Shenglong told Xinhua.
Wu Junyao, director of the natural resources and planning bureau of Zhaotong, told Xinhua that the disaster "resulted from a collapse in the steep cliff area atop the slope."
Two hundred rescue workers have been dispatched to the scene as well as dozens of fire engines and other equipment.
The site is covered in thick snow and rescuers are "using all kinds of tools to search for survivors," Xinhua reported.
Wu said the rescuers are digging through collapsed debris of "100 meters in width, 60 meters in height, with an average thickness of around 6 meters."
CCTV showed footage of rescue workers digging through twisted metal and concrete overnight in a bid to find survivors.
Other CCTV footage showed locals huddling for warmth around a fire in a shelter, eating instant noodles.
People from the surrounding area have chipped in to to help with relief efforts, state media said.
"Our main focus is on distributing supplies, cooking, and delivering food to those in need," Hong Jie, a 38-year-old resident of a nearby village, told Xinhua.
'All-out efforts'
Chinese President Xi Jinping Monday ordered "all-out" rescue efforts.
Landslides are common in Yunnan, a far-flung and largely impoverished region of China where steep mountain ranges butt against the Himalayan plateau.
Monday's disaster occurred in a rural area surrounded by towering peaks dusted with snow, state media footage showed.
China has experienced a string of natural disasters in recent months, some following extreme weather events such as sudden, heavy downpours.
Rainstorms last September in the southern region of Guangxi triggered a mountain landslide that killed at least seven people, according to media reports.
In August, heavy rains sparked a similar disaster near the northern city of Xi'an, killing more than 20 people.