According to media reports, a significant "bounce," - a shift in pressure that shoots rock from the walls with great force - killed the workers. A similar event is thought to be what trapped the original six miners.
MSHA stated that as a result of the Aug. 16 incident, rescue efforts have been suspended. Rescue attempts have been ongoing since the first cave-in on Aug. 6. The agency said it is unknown when rescue efforts would restart again. It also remains unknown whether the six miners are still alive.
Secretary of Labor Elaine Chao offered her sympathy to the families of the miners who were killed and injured.
“Our hearts, thoughts and prayers go out to the families, friends and colleagues of the rescuers who were killed and those who were injured last night during the heroic efforts to save the lives of the trapped miners,” she said.
It was not immediately clear where the miners who were killed on Aug. 16 were working or what they were doing when the cave-in. Crews have been drilling holes from the top of the mountain to try to find the miners while others were tunneling through a debris-filled entry to the mine.
Media reports also stated that as they were working underground, rescuers had advanced only 826 feet in nine days. Before the Aug. 16 cave-in, workers still had about 1,200 feet to go to reach the area where they believe the trapped men had been working.