2003 Ford Taurus Ses Recently Had Fire Under Hood Car Still Starts Runs There

I have a 2003 Ford Taurus ses and i recently had a fire under the hood the car still starts and runs there isnt any burnt wiring that i can see but every time i start the car there is white smoke comming out from the o2 sensor connected to the exhaust under the mannifold, there is also some kind of oil all over the bottom of the car. could the oil be what started the fire? and what could make white smoke come from the o2 sensor on the exhaust?