Dozens of miners have been trapped in a coal mine in China after a "rock burst", officials say. Four miners were killed and 50 more are missing after the accident, which happened late on Thursday in the city of Sanmenxia in Henan province. State media reported that the rock burst - an explosion caused by the sudden release of built-up pressure - happened shortly after an earthquake. Hundreds of Chinese miners die every year in pit accidents…But officials insist the country's record is improving, and say they have taken action by closing many illegal mines. A spokesman for the state-run Yima Coal Group, which runs the Sanmenxia mine…[said an] "intense search" was going on for the missing miners. [includes video report]