Powerful gusts pushed flames from a wildfire through Southern California canyons on Thursday, one of several blazes that burned near homes and forced residents to flee amid elevated fire risk for most of the region that prompted utilities to cut off power to hundreds of thousands.

The biggest blaze began late Wednesday as a house fire in Orange County’s Silverado Canyon, where gusts topped 70 mph.

“When crews arrived it was a fully engulfed house and the winds were extremely strong and they pushed flames into the vegetation,” said Colleen Windsor, a spokeswoman for the county’s Fire Authority.

The fire grew to more than 11 square miles and blanketed a wide area with smoke and ash.

Crews struggled in steep terrain amid unpredictable Santa Ana winds that sent flames racing across major roads. Two firefighters were hospitalized after being treated on scene for injuries, said Fire Chief Brian Fennessy. He said their condition was not immediately known.

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