The accident happened on Wednesday night at a mine in the northern province of Shanxi owned by Shanxi Datong Coal Mine Group, the official Xinhua news agency said, without giving further details.
The provincial Communist Youth League said on a verified social media account that 129 miners had been working at the time and 110 escaped, adding the cause was under investigation.
China is the world's largest coal producer, and deadly accidents in the sector are common.
Officials say the number of those dying annually in the country's mines has fallen substantially in the past decade, to fewer than 1,000 a year.
China has vowed to cut some two million jobs in its coal and steel industries, which suffer from massive overcapacity.
A senior manager at Shanxi Datong told AFP last year that the company had been forced to ramp up production to deal with a drop in coal prices.
At least 21 people died in a fire at a mine in the northeastern province of Heilongjiang in November.