BENTLY, Kan.  Teenagers driving through a field sparked a fire in northwest Sedgwick County.  Crews were called to the scene near 151st St. West and 93rd St. North around 1:30 p.m. Thursday.
     Investigators said the juveniles were driving in a nearby field, when the exhaust malfunctioned and started the blaze.  The teens tried to put out the fire themselves, but it quickly grew.
     A dozen crews were called to help get the flames under control. It took about an hour to contain the fire.  There were no injuries, and no structures were damaged.  It's not known how many acres burned.