Mother and her daughter wait for information about their loved one at Nuan'erhe Hospital in Chengde County

Twenty miners are now confirmed dead from Friday's gas explosion at a coal mine in northern China. And rescuers have now retrieved 40 bodies from a separate coal mine accident a day earlier.

Officials are investigating the cause of Friday's blast at Hougou Coal Mine, a government-owned operation in Shanxi province. The explosion triggered a second blast at the nearby Shapingzi Coal Mine.

Thursday, at least 40 miners died in a coal mine explosion in Chengde city, north of Beijing. Ten miners are still missing at the Nuan'erhe mine, which used to be state-owned but was privatized two years ago.

China's mines are the deadliest in the world despite a recent nationwide emphasis on enhanced safety procedures.