Updated 6:30 p.m.

Cal Fire says one of its firefighters died Thursday morning while battling the sprawling Thomas Fire in Ventura County.

Cal Fire Chief Ken Pimlott said in a statement the fatality involved a crew member from one of the agency's San Diego-based units:

I am very saddened to report that a firefighter fatality has occurred on the Thomas Incident. The incident is still unfolding, but in this world of fast moving information, it is important to me that only factual information be shared. To that end, I can confirm a fatality of a CAL FIRE Engineer from the San Diego Unit has occurred. Incident Management Team 4, Cal Fire Local 2881 and Southern Region leadership are working to support the Unit and his family, who have been notified.

Pimlott later identified the fallen firefighter as Cory Iverson, 32, an eight-year Cal Fire veteran. Pimlott said Iverson is survived by his wife, Ashley, who is pregnant, and a 2-year-old daughter.

Gov. Jerry Brown issued a statement saying he and his wife Anne were saddened by Iverson’s “tragic death.”

“His bravery and years of committed service to the people of California will never be forgotten,” Brown said.

Cal Fire did not immediately release details of the circumstances surrounding Iverson's death.

The announcement a firefighter had died came after reports of a "serious accident" that occurred as crews worked to contain the blaze on the outskirts of the town of Fillmore.

Unconfirmed reports from independent radio operators monitoring Cal Fire communications say that a mayday call went out about 9:30 a.m. from a crew battling the blaze on Grand Avenue, on the northwest outskirts of Fillmore. Reports relayed on Twitter say the fire overran the crew.

Fillmore is a town of 15,000 on the Santa Clara River, about 45 miles northwest of downtown Los Angeles. As the fire spread early Thursday, the Ventura County Sheriff's Office imposed a mandatory evacuation order on the unincorporated area just north of town.

The Thomas Fire started last week under unprecedented December fire weather conditions and continues to be driven through bone-dry terrain by gusty winds and extremely low humidity levels.

Illustrating the continued explosive nature of the blaze, firefighters were also faced with a major flare-up in the Rose Valley area northeast of the town of Ojai. Structures in the area were apparently threatened as the fire burned across Highway 33 north of Wheeler Springs.

All told, the blaze has burned more than 240,000 acres and destroyed more than 900 structures in Ventura and Santa Barbara counties since it began Dec. 4 near the town of Santa Paula. Cal Fire said early Thursday the blaze was 30 percent contained.