Gas floods sewer lines for two blocks around 48th Street and Correctionville Road after a Texaco gasoline truck was overturned.
The problem will only be a serious issue for two hours until the gas gets flushed away.
Gas is also on streets and ditches, so cars are being rerouted through side streets.
Four families evacuated because of sewer-line gas.
Fire Chief Charles Hochandel says: “The firemen followed catastrophe and hazmat procedures set up beforehand for just such an occurrence.”