Shortly after 2am Saturday morning firefighters were called to 198 Pratt Street (Off Oldfield Rd.) for a fire, all occupants of the building had been evacuated and waiting across the street.  When the arrived they found heavy fire on the first floor and quickly went to work within minutes.  We arrived at the scene within ten minutes from the call and the fire was out and they were checking for extensions.  Assistant Fire Chief Scott Bisson told me that the mother and son were checked out by paramedics and did not require medical treatment.  They will spend the night with relatives.  Bisson said the investigation to the fires cause  has just begun and that  it is too early to speculate a cause.