Updated:Rescue workers check their gear as they attempt to free Chinese miners trapped underground. Eighteen of the 28 workers in the coal mine in southwest Guizhou Province were killed in a gas explosion Saturday. Five miners in critical condition have been rescued. A local official says gas levels in the mine, as well as debris blocking the tunnel, are delaying efforts to reach five more trapped miners. China has a record of poor mine safety, with hundreds of accidents each year.