Crews are battling a monstrous fire in Des Moines, Iowa, that started overnight.

The fire broke out at the historic Younkers building at about 1 a.m. local time.

AMAZING RESCUE: Worker Dangles From Building Amid Massive Inferno

Portions of the building have collapsed, and firefighters are unable to enter the building due to the structural integrity. The building, which is more than a century old, was being remodeled.

About 90 percent of the city’s fire department has been called in to fight the fire.

Investigators are trying to determine what caused the massive fire.

No injuries have been reported.

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