The fire occurred just before 3 p.m. on Pistakee Lake in Fox Lake.
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Officials said when first responders arrived, the boat was engulfed in flames.
Boat catches fire on north suburban lake
A mother, father, and two children jumped into the water when the fire broke out.
The adults and one child were treated for minor burns there at the scene.
A child under the age of 10 was taken to the hospital with serious burns.
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The fire department put out the fire on the boat as it sank, from taking on so much water. Crews dragged the charred wreckage to shore.
Firefighters said the conditions on the lake created many challenges.
"The boat itself was drifting, also with the wind, and it started drifting toward another row of boats at that marina.," Fox Lake Fire Protection District Lieutenant Jake Geist said. "Luckily though, the wind pushed it away from those boats and then our boat was able to extinguish it before it got to any other boats."
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