Omaha firefighters ordered the evacuation in case fumes got into the building's ventilation system.
Battalion Chief Rob McAvoy tells 1110 KFAB a loading dock worker discovered a broken container of nitric acid around 10:15 Friday morning.
Hundreds of employees were then evacuated from the 40 story building in case the fumes got into the ventilzation system.
The acid poses a respiratory hazard. McAvoy says it appears the container began leaking during shipping. Hazardous materials crews wearing protective suits removed the acid. No one was injured.
The all clear was given around 11:30.