Janesville fire officials are looking into the cause of an early morning residential fire on the city’s northeast side.  Firefighters responded to a duplex in the 2900 block of Randolph Road about 1:30 a.m Monday.  Officials say, upon arrival, firefighters found the garage to be fully engulfed with flames extending into the home.  Damage is estimated at more than $300-thousand.  No one was hurt, but the home is considered uninhabitable and the Red Cross is assisting the residents.