Janesville firefighters may never know the cause of a blaze at the city’s landfill.  Firefighters were called to the northeast corner of the landfill on Black Bridge Road just before 4:30 p.m. Thursday.  First responders say they could see the smoke as the left the station, and witnesses report seeing the smoke from Edgerton.  Departments from Milton, Evansville, and the Town of Turtle helped haul water.  Officials say the fire consumed about two-acres.  Landfill personnel worked with firefighters in moving debris to help extinguish the fire.  Firefighters were on scene for more than four-and-a-half hours.