Investigators were looking into the cause of the Friday night blast in Yunnan province, the Xinhua News Agency said Saturday.

China has the world's deadliest mines, where explosions, cave-ins and floods killed nearly 3,800 people last year.

Coal accounts for about 70 percent of electricity production for the booming economy. But efforts to improve safety have been frustrated by lax enforcement, weak safety regimes and corruption among local officials and mine owners chasing profits.