The blast came about two hours after firefighters were called to extinguish a fire in the concrete silo at Hoge Lumber Co.
Two firefighters were atop the 70-foot-tall silo. A firefighter in an aerial bucket was thrown to the ground.
The blast blew off the top of the silo, with chunks of concrete flying across the road into a cemetery about 100 yards away. The debris caused some of the injuries. Eleven people were taken to hospitals.
Firefighters were hosing down dust in the silo to avoid an explosion when it blew up. The dust silo feeds the boiler for the lumber company. The silo was filled with wood shavings and sawdust. The family-owned business bills itself as the world's largest maker of wood bowling lanes and has been in business since 1904. It also makes cabinetry and building supplies.
The operation also recycles wood chips and other byproducts that are fed into its generator that supplies power to the plant and all of the village of New Knoxville, which has about 900 residents and is about 50 miles north of Dayton.