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Firefighters are on the scene of a gas explosion and massive fire Tuesday night, Feb. 19, 2013 at JJ's restaurant at the Country Club Plaza in Kansas City, Mo. A car crashed into a gas main in the upscale Kansas City shopping district, sparking a massive blaze that engulfed an entire block and caused multiple injuries, police said. (AP Photo/The Kansas City Star, Tammy Ljungblad) KANSAS CITY OUT

Kansas City gas explosion

A day after a natural gas explosion

leveled a popular restaurant, investigators raced to search the rubble

and tried to understand how the blast happened despite suspicions that

flammable fuel had been leaking, maybe for weeks, somewhere in the busy

outdoor shopping area.