A static or dust explosion is viewed as the possible cause of a fire on Tuesday morning at an Apple Valley, CA cement factory that left two firefighters injured, the Victorville [CA] Daily Press reported Tuesday.

Four engines from Apple Valley Fire Protection District (AVFPD) and two engines from San Brenardino County Fire Department responded to a report of an explosion with fire at the Cemex Cement Factory at 25220 Black Mountain Quarry Road in Apple Valley at about 2:30 am, according to a post on the AVFPD’s Facebook page and the Daily Press report.

Jason Nailon, fire marshal of the AVFPD told the Daily Press that alternative fuels used to power the plant’s kilns – composed of wood chips, pistachio shells, and tire clippings – was involved in the fire. The AVFPD’s Facebook post on the incident noted that “dust and debris on the metal trusses” were a factor in the fire, and that the sprinkler system had held the fire “in check.”

“When we got there, the fire was almost out because of the sprinkers,” Nailon told the Daily Press, “but the rafters appeared to be burning. It turned out to be an accumulation of dust up on the rafters that was still burning.”

The fire was extinguished in about two hours, the AVFPD said. Two firefighters were minorly injured during the incident, the Daily Press reported, with one reporting an ankle injury and another who suffered from heat exhaustion.

The estimated cost of the damages is unknown.