The accident took place at around 3 p.m. (07:00 GMT) near the city of Yibin, China’s CCTV news channel said. A search-and-rescue operation is underway.
Mine accidents are not uncommon in China. A roof collapse in Shaanxi province in January killed 21 people.
The same number of miners died in Shandong province in October of last year when a rock burst destroyed a tunnel.