CAL FIRE Spokesman Robert Foxworthy confirms 5 ambulances were called to the Sonoma County Fairgrounds and were being evaluated at the CAL FIRE base camp in the Santa Rosa fairgrounds.
Officials say the carbon monoxide exposure occurred off-site from the fire area and did not disclose the source.
SKY7 was above the Sonoma County Fairgrounds where firefighters have been staying while battling the Glass Fire burning in Napa and Sonoma counties.
CAL FIRE says one firefighter was transported to a local hospital for further evaluation.
The other firefighters have since been released.
Stay with ABC7 News for the latest details on this developing story.