A fire in a large commercial building in Danbury has been extinguished.  Danbury Fire Department responded to a building on Augusta Drive, in the corporate park section of the City around 1am yesterday.  The incident escalated to a second alarm, bringing in assistance from Brookfield Volunteer Fire Company Tower and Ridgefield Fire Department.  The flames in the rear of the building extended into the roof area.  The scene required an extensive overhaul. The Danbury Fire Marshal's office is investigating the cause which is undetermined at this time.