For the sake of documentation, here's the definition from Wikipedia:

The Sago Mine disaster was a coal mine explosion on January 2, 2006 in the Sago Mine in Tallmansville, West Virginia, USA that trapped 13 miners for nearly two days. One miner survived. It was the worst mining disaster in the U.S. since a 2001 disaster in Alabama killed 13, and the worst in West Virginia since a 1968 disaster that took 78 lives.