The cause of a residential fire in the 400 block of Wilson Avenue in Janesville is under investigation. Battalion Chief Ryan Murphy says firefighters responded to the single story home a little after 3:30 a.m. Saturday morning. Murphy says the fire appears to have started in the area of the porch and worked its way inside the home. He says a father and two children were alerted to the fire by smoke detectors and escaped. The did need to be treated for smoke inhalation on the scene. The home is considered a total loss. The Red Cross is assisting the family.