An apparent blast at a coal mine in northern China killed 21 workers, AP quoted a state news agency as saying Sunday. Four miners were rescued by emergency workers, Xinhua News Agency said. Seven managed to escape on their own after the accident Saturday at the Wujiu coal mine outside Datong city in Shanxi province, it said. All of the victims died of carbon monoxide poisoning, Xinhua reported, citing an unidentified city official. The number of miners underground at the time of the accident was not known and rescuers were continuing to search, it said.