Ambulances were called to a Thanksgiving party in Chicago Thursday night after 20 people suffered carbon monoxide poisoning caused by a grill being used inside the property.

Seven people were transported to nearby hospitals in good-to-fair and fair-to-serious conditions, a Chicago Fire Department spokesman told the Chicago Tribune.

The other 13 victims were treated at the scene.

Carbon monoxide can't be smelled or seen, but at high levels can be fatal.

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