Watertown Fire Rescue responded to the report of a semi fire pulling a fully loaded grain trailer of corn, in the area of 177th St and 465th avenue. Upon arrival on scene fire crew found a 1991 Freight Liner cab over semi with light smoke coming from underneath the cab. Fire personal used a thermal imaging camera to identify two hot spots and used a pressurized water can to cool those spots. At the time of extinguishment the cause of the fire was unknown.