MADISON, Wis. -

Madison Fire Department's hazardous materials team was called to an office building on the city's west side Monday afternoon after occupants reported trouble breathing and hives.

Crews responded to 583 D'Onofrio Drive at 1:44 p.m. for a report of a strong odor in the building.

Occupants evacuated the building and met the firefighters when they arrived. Seven of the occupants reported feeling ill, but their symptoms eased once they got into fresh air. None required transport to a hospital, according to a Madison Fire Department news release.

Firefighters noted heavy fumes on the second floor, with monitors verifying the poor air quality.

Upon investigation, the hazmat team found a tenant on the second floor who had been painting a wall using a paint containing isocyanates. Isocyanates are the raw materials that make up all polyurethane products. Isocyanates are thought to be a sensitizer and can cause allergic reactions, according to the news release.

The paint contained cautionary warnings about inhalation and was to be used in a well-ventilated area.

Fire officials said it was used in an enclosed office space, and the windows in the building cannot be opened.

Fumes from the paint had entered the building's ventilation system and spread throughout the second floor, according to the release.

Fire crews advised the occupants that the atmosphere was most likely safe. They were allowed to return to the building, but they were cautioned to be alert to any reactions and leave the building if symptoms returned, according to the release.