What is that smell? Chicago-area residents report mysterious odor

Residents across parts of the Chicago area reported an unexplained chemical or burning electrical odor lingering in the air for more than 12 hours, prompting monitoring efforts by local fire officials.

What we know:

The Algonquin/Lake in the Hills Fire Protection District said it has received multiple 911 calls describing the odor, which has been reported across a wide area stretching from central Illinois through Indiana and as far north as the Wisconsin border. 

Officials said the smell appears to be originating from a location "quite south" of Algonquin, which is roughly 40 miles northwest of Chicago, though its exact source remains unknown.

Fire officials said they are actively coordinating with regional partners and other agencies to determine the cause and track any potential public safety concerns. 

What you can do:

Authorities urged residents who experience symptoms such as difficulty breathing, dizziness, nausea or irritation to seek medical attention. Officials stressed that 911 should only be called in the event of an immediate emergency or life-safety concern.

The fire district said it will provide updates as more information becomes available.