Naperville and portions of Aurora, Glen Ellyn and Oswego -- as well as towns as far east as Evergreen Park and Oak Lawn -- stink, and no one seems able to figure out why.
Authorities still had no explanation Monday night for the olfactorily offensive odor of sulfur that has permeated portions of the Chicago area over the past two days.
The problem appears to be most acute on Naperville's far southwest side, where more than a dozen homeowners have complained since Sunday afternoon of a rotten-egg-like stench in their neighborhoods. Afflicted areas have included Fesseneva Lane and the 2800 block of Fairhauser Road, both in the Harmony Grove area.
At least four people complained Sunday of the smell of sulfur near their homes, according to police and fire emergency radio broadcast reports.
Larry Deguisne, EMS bureau chief of the Naperville Fire Department, said 10 additional 911 calls were logged Monday from similarly concerned citizens, with fire crews sent to investigate three of those complaints. No emergency situations resulted from any of the calls, Deguisne said.
Homeowners, in most instances, have expressed fear of a natural gas leak. Because natural gas is odorless, many utility providers augment it with mercaptan, a non-toxic chemical that gives the gas its sulfuric scent.
Tom Kallay, community relations director for Naperville-based Nicor Gas, confirmed Monday that company officials have heard complaints from residents and police and fire officials in Naperville, Glen Ellyn and southwest suburban Oak Lawn and Evergreen Park.
A Nicor dispatcher also fielded three telephone calls late Monday afternoon concerning "a gas odor moving from Oswego toward Aurora," he said.
Kallay added, however, that not a single open or ruptured gas main has been found during the investigations of any of the complaints.
"I can't tell you what the source is, but I can tell you definitively that Nicor doesn't have anything going on right now," where punctured gas mains or similar emergencies are concerned, Kallay said.
"We're not quite sure what (the problem) is," he said.
Deguisne added the city of Naperville has no construction or earth-moving projects under way that might be connected to the source or cause of the odor.
A spokeswoman for the Illinois Environmental Protection Agency did not return a telephone message Monday night that sought comment on the situation.