A mysterious odor sparked dozens of calls from residents in several Chicago suburbs Tuesday evening and officials believe they have determined the cause of the smell.
In several north, northwest and far western counties in the Chicago area, officials said reported receiving an influx of 911 calls related to a natural gas smell.
The Lake County Sheriff's office said it was "fielding numerous 911 calls regarding a natural gas leak in the area."
Officials in Crystal Lake, Marengo, Belvidere and Lakemoor acknowledged that residents had reported the smell of natural gas or "rotten egg."
"We have had multiple reports of the smell of natural gas in the area. This appears to be a widespread issue across all of Belvidere and Nicor is investigating," the Belvidere Fire Department wrote on Facebook. "If you smell natural gas outside there is no need to call it in at this time. If you have a natural gas smell INSIDE your home or building please call 911."
According to the Ogle County Sheriff's Office, officers also received numerous calls from throughout the county reporting the odor of natural gas Tuesday evening.
Officials later determined that the odor was believed to have come from "maintenance of equipment located in Cedar County, Iowa," which later drifted into the Chicago area.
A spokesperson for Nicor Gas told NBC Chicago that a "spillage" occurred in Iowa, with eastern winds carrying the odor over to the far western suburbs.
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"The odor that is being smelled is called Mercaptan, which gives a 'rotten egg' odor. Mercaptan is not a hazardous chemical and doesn’t pose a risk to public safety," the city of Marengo wrote on social media.
A press release from the Clinton County Sheriff's Office in Iowa confirmed that authorities responded to calls of a natural gas odor in DeWitt, Iowa, shortly after 10:30 a.m. on Tuesday and began investigating.
Following an investigation, Clinton County officials believe the smell originated from maintenance of equipment in Cedar County, Iowa, located just west of Clinton County.
Officials said there is no threat to the public as the smell dissipated Tuesday evening.
