Fifteen firefighters battling the Glass Fire in Wine Country have recovered and are back on the fire lines after being exposed to carbon monoxide early Tuesday.
One firefighter has been taken to a local hospital for further evaluation.
Their condition isn't known at this time.
CAL FIRE told KCBS Radio's Jeffrey Schaub the incident happened while the firefighters were working in an active fire zone. They were brought back to CAL FIRE’s base camp, located at the Sonoma County Fairgrounds in Santa Rosa.
The carbon monoxide is thought to have come from chemicals or machinery that omit the gas once combined with flames, however, it could have also come from a fire truck.
"Specifics are still pretty vague right now," CAL FIRE Spokesperson Robert Foxworthy said. "We're still in the investigative phase. We have a number of firefighters that were presumably exposed to carbon monoxide and are currently being evaluated."
Carbon monoxide poisoning symptoms include headaches, dizziness, vomiting, loss of consciousness or even death.
Over 2,000 firefighters are working the Glass Fire. Most are in Napa County.