Here's a grain elevator story, but sawdust can do the same thing. When the air gets dusty enough, KABOOM!

WICHITA, Kan. (Reuters) - At least two workers were killed and several more were missing after an explosion ripped through one of the largest grain elevators in North America Monday, fire department officials said.

Six or seven employees were missing after the huge blast rattled the area around the giant elevator, which is about 5 miles south of Wichita. They could be trapped in tunnels and rooms beneath the rubble, the officials said.

A local television station said three other workers were critically burned in the blast, which struck the north end of the facility.

A helicopter plucked five workers to safety after they were stranded on the roof of the partially demolished structure.

The owner of the elevator, Debruce Grain of North Kansas City, Missouri, said it dispatched a rescue crew to the scene. The elevator can hold 20 million bushels of grain.

A mere spark can ignite the highly flammable grain dust in elevators, and workers normally take precautions to dampen down the dust.