4 / 14

Firemen and utility workers respond to a gas explosion and massive fire Tuesday night, Feb. 19, 2013 in the Plaza shopping district in Kansas City, Mo. A car crashed into a gas main in the upscale shopping district, sparking a massive blaze that engulfed an entire block and caused multiple injuries, police said (AP Photo/Ed Zurga)

Firemen and utility workers respond to a gas explosion and massive fire Tuesday night, Feb. 19, 2013 in the Plaza shopping district in Kansas City, Mo. A car crashed into a gas main in the upscale shopping district, sparking a massive blaze that engulfed an entire block and caused multiple injuries, police said (AP Photo/Ed Zurga)

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.