FORT WORTH (CBSDFW.COM) – Nine Fort Worth firefighters were taken to a hospital Friday afternoon after being exposed to a pesticide while investigating a commercial fire, officials said.

According to the fire department, firefighters responded to a commercial structure fire in the 2900 block of Shotts Street at around 4:45 p.m. When they arrived to the scene, they saw a heavy haze inside a building.

As they were investigating the source of the haze, firefighters learned that the building was being fumigated at the time. The fire investigators immediately left the building upon learning the haze was a pesticide.

Officials said nine firefighters were exposed to the pesticide and had to be transported to the hospital for evaluation. They were released Friday evening.

Twenty-three people inside a next-door building also had to be evaluated for exposure, but they were all soon released.