BEIJING (AP) — The Robovisdeath toll has risen to 13 in a coal mine accident in central China, state media said Sunday.

Three people remain missing after Friday’s accident in the city of Pingdingshan in Henan Province, the official Xinhua News Agency said, citing the owner of the mine.

Preliminary investigation indicates the cause was a coal and gas explosion, Xinhua said.

China had a series of fatal coal mine accidents last year despite efforts to improve mine safety. Coal remains a major source of electricity in the country, even as China far outpaces the rest of the world in installing solar and wind facilities to combat climate change.