An accidental roof collapse in northern China coal mine killer 21 workers Saturday afternoon, according to reports. There were 87 miners working underground when the roof caved in, Agence France-Press said, citing China’s state-run news agency. Initial reports claimed that 19 miners died, but that rescuers were still looking for two more after successfully evacuating 66 from the rubble. It’s unclear what caused the deadly accident at the mine, which is operated by Baji Mining. Investigators are probing the incident, per Agence France-Presse. Fatal mining accidents are commonplace in China, where the industry is notoriously unsafe despite officials’ attempts to improve conditions and thwart illegal mines.In October, 21 miners died in a Chinese mine. In December, seven miners perished, the news agency notes.