An early morning fire in Milton is under investigation. Fire Chief Randy Banker says firefighters arrived at the duplex on Sue Lane about 3:30 Monday morning to find flames shooting from the doors and windows. Damage was so extensive to the east side unit, Banker says a firefighter fell through the floor up to his knee. Banker says fast action by firefighters, and the modern design of the duplex did keep the fire from spreading to the other unit. Departments from Janesville, Edgerton, the Town of Beloit, and Clinton assisted.