Officials in the western Iowa city of Council Bluffs have issued a boil advisory, warning people against drinking city water or cooking with it.
Officials feared that a drop in pressure from a water main break early Wednesday morning could have allowed contaminants to reach the water, posing a health risk.
Several stores reported running out of bottled water.
The break caused street flooding in the area and created a large crater that one man drove his car into. The man wasn't injured, and a tow truck removed the car from its predicament.