The giant wildfire burning at the edge of Yosemite National Park is 23 percent contained, U.S. fire officials said Wednesday

The U.S. Forest Service said the fire has now consumed 293 square miles (758. sq. kilometers).

The fire in northern California had destroyed 111 structures and threatened water supplies, hydroelectric power and giant sequoia trees — a state icon — as of late Tuesday. Some 4,500 structures remained threatened.

The fire, one of the largest in state history, has caused air pollution problems in California cities far from the scene.

Forestry experts said unnaturally long intervals between wildfires and years of drought primed the Sierra Nevada mountains for the explosive fire in the rugged landscape.

Federal forest ecologists said historic policies of fire suppression to protect timber interests left a century’s worth of fuel in the fire’s path.

Two years of drought and a constant slow warming across the Sierra Nevada also worked to turn the Rim Fire into an inferno.

For years, forest ecologists have warned that Western wildfires will only get worse.

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Photo Credit: The Rim Fire burns through trees near Yosemite National Park, Calif., on Tuesday, Aug. 27, 2013. Jae C. Hong / AP Photo