Residents across the Chicago area have been flooding emergency lines over the weekend, reporting a mysterious chemical odor lingering in the air. The exact source of this smell remains a mystery, according to local authorities.

The Algonquin-Lake in the Hills Fire Protection District has confirmed that they’ve received numerous 911 calls regarding an unfamiliar odor, which has been variously described as resembling chemicals or burning electrical components.

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These reports began pouring in from late Saturday night into Sunday morning, covering a vast region that stretches from central Illinois, through Indiana, and reaching up to the Wisconsin border.

While the origin of the odor seems to be quite a distance south of the Algonquin-Lake in the Hills area, officials have yet to pinpoint its exact source.

The fire protection district is actively monitoring the situation and collaborating with regional agencies to determine the cause of the smell.

Authorities advise residents to seek medical help if they experience symptoms such as breathing difficulties, dizziness, nausea, or irritation.

Call 911 only if there is an immediate emergency or life-safety concern, officials added.

Further information was not immediately available.