The fire broke out before 8 p.m. Tuesday in the 2000 block of West 37th Avenue in Hobart, Indiana, fire officials said.
Flames could be seeing shooting through the roof of the barn.
The fire department says there were hazardous items inside, including propane tanks and welding equipment that added to the danger.
Several neighboring fire departments aided in the response.
No one was hurt.
The fire remains under investigation.