On Thursday, July 10, 1902, at approximately 11:00 a.m., a powerful explosion occurred in the Klondike section of the mine, and ultimately 112 miners, 84 of whom were immigrants from England, Poland and Slovakia, lost their lives. The explosion was attributed to what miners refer to as firedamp, a methane gas mixture. Killed immediately were those miners working in the Klondike section. Many other miners, as well as the vast majority of mine animals, were killed by an asphyxiating gas called afterdampthat sprea