WHILE DRIVING THE OPERATOR SMELLED SOMETHING HOT. UPON STOPPING AND EXITING THE VEHICLE THE OPERATOR SAW FIRE COMMING FROM BEHIND THE MOTOR COMPARTMENT THROUGH THE WHEEL WELL. HE WAS ABLE TO EXTINGUISH THE FIRE.*AK OUR MECHANIC INSPECTED THE VEHICLE AND DISCOVERED THAT THE CLAMPS HOLDING THE POSITIVE AND NEGATIVE BATTERY LEADS HAD WORN THROUGH THE INSULATION CREATING A DEAD SHORT. THE SAME DEFECT WAS DISCOVERED ON ANOTHER OF OUR SCHOOL BUSES THAT HAD BEEN PURCHASED AT THE SAME TIME.