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Two people were killed in an explosive wildfire burning south of California's Sierra Nevada mountains Friday in classically terrible wildfire fighting conditions: hot, dry and rugged.

The wildfire, dubbed the Erskine fire, began near Lake Isabella on Thursday amid temperatures in the 90s and a staggering lack of humidity. It ballooned from 5,000 acres to 30,000 acres by Friday night, according to the Central California District Bureau of Land Management.

The fire had already engulfed 100 homes and another 1,500 were at risk, according to the Kern County Fire Department.

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The department announced Friday afternoon that two people had been killed in the blaze. No other details were immediately released.

Gov. Jerry Brown issued a state of emergency in Kern County Friday afternoon so that additional resources could be funded and sent there. "We join all Californians in expressing our gratitude to the courageous firefighters, emergency personnel and volunteers working tirelessly throughout Kern County to help residents and extinguish this fire," Brown said in a statement.

“The destruction is just immeasurable … I've never been on a fire where we've lost this many homes,” said Kern County Fire Department Capt. Tyler Townsend, who has been in the area for nearly a decade. Townsend told NBC News that some of the homes exploded, “and you could hear that from miles away.”

Rugged terrain and stifling heat were posing a challenge to firefighters, who Townsend said had to strategically decide when to protect a home and when to divert resources elsewhere.

“There’s so many homes and you have to triage — what can you save and what do you have to just let go. That's actually, it's hard to do, it's hard to pull away from a home that you want to save but if you spend too much time on that home, you're gonna lose five others,” Townsend said.

The National Interagency Fire Center said that the toll of decimated houses made the fire the most destructive of the season. At Least nine communities were under mandatory evacuation orders, and parts of Hwy 178 were closed due to the fire, which was 5 percent contained as of 6:23 p.m. local time Friday (9:23 p.m. ET).

More than 800 firefighters were assigned to the Erskine Fire, and more were on the way to combat the flames on the ground, with air tankers and helicopters. Three firefighters have suffered smoke inhalation injuries, according to officials.

Meanwhile, 1,200 firefighters were working to quell the San Gabrial Complex fire, 400 miles to the south near Los Angeles.

The fires had burned more than 5,200 acres and was 30 percent contained, officials said Friday.

More than 1,300 homes have been evacuated during the 4-day-old blaze, but about half of the residents were allowed back as crews made headway due to cooler weather.