TAIYUAN, May 18 (Xinhua) -- At least 15 miners are trapped underground after a coal mine explosion in Yu County, in north China's Shanxi Province, Monday afternoon, local authorities said Tuesday. The gas explosion occurred at 4:30 p.m. at the Chengdong Coal Mine. Rescue work and an investigation are underway, said a spokesman for Yangquan municipal government, which administers Yu County.