Abstract: At 7:54 a.m. on January 7, 1998, Employees #1 through #4 were about to begin work in the production room at Sierra Chemical's Kean Canyon explosives manufacturing facility when two large blasts involving over 40,000 lb of explosives rocked the facility. All four workers were killed. The facility melted, mixed, and poured cast boosters in two separate production areas using large stainless steel steam-and-hot-water-heated melting and mixing kettles. The production room had been in service for less than four months and had several substantial changes compared to the old production area, including kettles heated by steam as opposed to hot water and direct drive mechanical agitation instead of hydraulic agitation. Possible causes of the explosions include raw material contamination, a cold start, or static ignition.