An outburst of poisonous gas at the Xilutian Mine in Fushun, a city in Liaoning province, took place Saturday when 50 miners were working underground, the official Xinhua News Agency reported.
The miners were about 400 meters from the entrance of the shaft, and 15 workers were instantly killed, while the rest managed to escape.
The cause of the accident was under investigation.
China's mines are the world's most dangerous, and thousands of miners are killed every year in fires, explosions and floods. The lack of safety equipment and lax regulations are often to blame.
A massive blast at a coal mine in the central province of Henan left 148 miners missing on October 20. Rescuers found 141 bodies while the remaining workers were unlikely to have survived.