Fire investigators say Representative Craig Hickman was using gasoline to start the fire and gas fumes caused his clothing to catch fire.
It happened around 9:30 this morning behind Hickman's home on Annabessacook road.
Officials say Hickman was burned on his legs and chest.
A friend attempted to drive him to the hospital, but stopped at the Winthrop fire station to ask for help.
He has since been airlifted to Maine Medical Center for treatment.
Investigators say Hickman poured a small amount of gasoline on the brush pile and then lit a cardboard egg carton before placing it on the fire.
That's when the gas vapors exploded.