At the time of the Wednesday explosion, 154 miners were reportedly working in Sichuan province’s Xiaojiawan mine.
Twenty-one remain trapped.
According to official state news agency Xinhua, temperatures have reached 80-90C and carbon monoxide is dense in the zone where the surviving miners are trapped.
Only a few masked rescue workers have been able to enter.
Xiaojiawan is owned by Zhengjin Industry and Trade Company in Panzhihua, 750km southwest of the provincial capital of Chengdu.
The mine’s owner is under police custody.
The news follows local media reports of an unspecified accident at the city of Changji's Hongxing coal mine where six miners were killed and six more injured on Tuesday.
On Monday, 10m of roof collapsed at the Nuanquan operation in Shanxi province where efforts to rescue seven trapped miners are ongoing.
The string of incidents has sharpened government focus on the dangerous nature of China’s small coal mines.
The State Administration of Work Safety last week said it planned to reduce the number of fatalities by closing more than 600 small mines.