YINCHUAN -?Two workers remain missing after an explosion killed 18 people at a coal mine in northwest China's Ningxia Hui Autonomous Region, rescuers said Thursday.
The explosion at 7 a.m. Tuesday at a small coal mine, which belongs to Linli Coal Mining in Shizuishan City, left 18 workers dead and two missing.

Rescue efforts were hampered by waterlogging and a high concentration of gas. Rescue workers will continue searching for those missing, after draining water and gas from the shaft.
An initial investigation showed that the explosion was caused by illegal mining. The company owners are in police custody.