The rest of the home had moderate smoke damage.
The fire broke out around 3:30 p.m.in the City Place Development, a $450 million project filled with luxury apartments and amenities, according to the Kansas City Star.
Residents in a Kansas City suburb are assessing the damage after an eight-alarm fire destroyed two dozen homes.
"Investigators are confident the fire was caused by the accidental ignition of wooden building material ignited by a welder conducting hot work on the site", said Mark Sweany, Overland Park Fire Marshal.
Much of the damage to the homes was caused by heat exposure and flying embers, according to Overland Park Fire Department spokesman Jason Rhodes, who described the scene as "a bit of a war zone" earlier.
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Police received a call about 7 a.m. from a relative asking officers to check the welfare of the victims, according to Sgt. A neighbor of the home on 35th Avenue, said a couple with two children, a girl 14 and a boy 11, lived at the house.
The Overland Park Fire Department has provided video of Wednesday morning's fire.
Ken Block of Block Real Estate, the CityPlace developer, said in a statement that the company is grateful for all the fire departments for "their heroic efforts". Rhodes said three firefighters were treated for minor injuries, but added that it was a "huge blessing" that none of the injuries were serious.
"Out units stood by in a designated staging area in preparation to support fire suppression activities", she said.
2alarm fire building under construction college & Nieman. "They're breaking out quickly", Rhodes said.
Officials said about 40 fire personnel from the arson task force, Alcohol, Tobacco, Firearms and Explosives and state investigators will come in to inspect the homes and construction that were impacted.