Firefighters were already on the scene, anticipating that smoldering debris could reignite.
The fire that required fully a third of Chicago's fire-fighting force Tuesday night rekindled Thursday morning.
Images of the abandoned warehouse in the Bridgeport suburb on the city's South Side showed flames again shooting through the roof and smoke pouring south as fire equipment gathered at the building. The flames began again just before 6 a.m., according to NBC 5.
Chicago Fire officials called it a "significant rekindle," the affiliate reported, adding that crews on the scene were already expecting it.
A rarely-used "deluge unit was called in to help fight the fire — a vehicle with large plumbing to allow several hose lines to feed a single nozzle to combine lines for high volume," Chicago Fire Media tweeted, according to NBC 5.
"We know that we still have buried debris that's burning. The hose lines are not capable of getting at it," Dep. Fire Commissioner John McNicholas said the day before.
With temperatures still hovering around 10 degrees, the debris continued to smolder through Wednesday as bundled up firefighters poured water on hotspots within the warehouse's frozen facade.
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