LA CROSSE, Wis. (WKBT) -

A Mercaptan leak at Kwik Trip's fueling facility in the industrial park on La Crosse’s North side caused a strong odor in the city, according to the La Crosse Fire Department.

Natural gas is odorless and Mercaptan is the odorant that is added so residents can identify the gas during a leak, firefighters explained. The odor is similar to sulfur or rotten eggs.

Calls from residents started coming to the Emergency Dispatch Center at about 7:45 Friday morning. Homeowners called from Gillette Street on the North side and throughout the South side of La Crosse.

While the cause of the odor is not associated with Xcel Engery natural gas facilities, the company still encourages residents to call 1-800-895-2999 to report a gas odor. For more information on natural gas safety, go to Xcel Energy's website, xcelenergy.com.