Most of the town of 1,900 was emptied about 9 a.m. CST when a blaze in a warehouse at the local airport sent smoke billowing overhead, the Des Moines Register reported. The townspeople were give the all-clear sign shortly after 3 p.m.
Iowa State Patrol Sgt. Scott Bright said tests showed Northwood's air was safe after the plume of smoke had moved away to unpopulated areas, the newspaper said.
The warehouse stored materials used for crop dusting, but authorities determined there may not have been as much sulfuric acid involved as originally feared, the newspaper said.