Officials with Sequoia and Kings Canyon National Parks say that a tree fell and hit four people around 3 pm on Thursday in the southern end of the fire.
Action News was there as one of those helicopters landed at Community Regional Medical Center in Fresno.
Here's what came over the police radio moments after the tree fall, "Firefighter involved in a tree accident, tree did hit her in the head. Looks like injuries noted are weakness by lateral upper extremities, more so in pain in the right arm. She did have positive loss of consciousness, unknown for how long. She also did have vomiting and um nausea and she has a headache at this time."
Officials say they suffered serious injuries, but are receiving care and are expected to survive.
On Friday morning, the four personnel members were released from the hospital. Officials say one of the victims was a CAL FIRE employee and the other three were members of the California Conservation Corps.
The KNP Complex Fire has charred more than 86,000 acres with little containment.