As schools, apartments and nursing homes were built around the plants, "safety never crossed our minds, " Mr. Nors said.

WSJ: Fertilizer-Storage Risk Is Often Overlooked

Matt Nors, 30 years old, owner of the Nors Sausage and Burger house on Main Street, said he didn't think any of the workers were in the plant during the explosion.

WSJ: Fertilizer-Storage Risk Is Often Overlooked