LOS ANGELES (CBS SF/AP) — A firefighter assigned to the huge wildfire burning in Southern California has died.

The firefighter was a Cal Fire engineer from the San Diego Unit battling the Thomas Fire, according to Director Ken Pimlott.

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“Please join me in keeping our fallen firefighter and his loved ones in your prayers and all the responders on the front lines in your thoughts as they continue to work under extremely challenging conditions,” said Pimlott.

The circumstances of how the firefighter died was not disclosed. His name was not released.

More than 8,000 firefighters are working on what is now the fourth-largest wildfire in California history, covering 379 square miles (982 square kilometers), in Santa Barbara and Ventura counties.

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The cost of battling the Thomas Fire is approaching $75 million.

Some evacuations have been lifted, but authorities say seaside towns including Montecito and Carpinteria remain under threat. The fire is 30 percent contained after destroying 970 structures.

The National Weather Service says extreme fire danger conditions from dry Santa Ana winds could last through the weekend.

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