Embers from a bonfire set fire to outbuildings on a property in Freiston Ings yesterday (Monday) evening.
Wholetime and retained fire crews from Boston were sent to the incident shortly after 6.30pm.
Lincolnshire Fire and Rescue say the blaze involved a derelict outbuilding on Bankhouse Farm Lane.
It says there was severe fire damage to outbuildings and moderate damage to a nearby conservatory.
Crews wearing breathing apparatus used two hose reel jets to put out the fire.
Lincolnshire Fire and Rescue said the blaze was started by embers from a nearby unattended bonfire.