Crew members working near a flare-up on the remaining fire line at the Cedar Fire on Tuesday were forced to deploy their fire shelters to protect themselves from flames.
Bureau of Indian Affairs spokeswoman Candy Lupe said none of the firefighters suffered life-threatening injuries, and once the area cooled off they were able to walk out.
It is unclear at this time what may have caused a sudden change in fire activity.
Lupe said a shelter deployment "is considered a serious incident in the wildland firefighting community", and officials will investigate.
The incident comes near the three-year anniversary of the Yarnell Hill Fire, where 19 firefighters had to do the same thing, but lost their lives.
The Cedar Fire has burned 45,918 acres near Show Low since it was sparked on June 15, and remains 75 percent contained.