Janesville firefighters are looking into the cause of a house fire on the city’s north side.  Firefighters were called to the 1000 of Milton Avenue about 10:45 p.m. Tuesday.  The first to arrive found light smoke on the second floor of the two story residence and a small fire in the attic.  Two adults and two children had already escaped safely.  The fire was quickly extinguished.  Damage to the structure is estimated around $10,000.  The Red Cross is assisting the family.