At least 300 people were evacuated from a building on the Nebraska Medicine campus on Tuesday morning.
Firefighters at the scene say there is an irritant in the air near the Durham Outpatient Center.
At first it was thought that it was coming from an elevator shaft, but Omaha Fire told KMTV reporter Emily Szink that paint in the parking garage was the cause of the issue.
Officials added when mixed with high temperatures and humidity this can sometimes be a problem.
At least two people are being treated for injuries.
Before noon, crews were turning back the air at the Durham Outpatient Center to check air quality.
Before 3;00 p.m. Officials said the Durham Outpatient Center (DOC) and adjoining parking structure at are back open.
Nebraska Medicine officials said that all appointments at the Durham Outpatient Center were canceled for the day due to odors from painting in the parking garage.
They added that they will reschedule those appointments by phone.