An early Monday morning fire heavily damaged a storage building at Blackburn Correctional Complex in northern Fayette County.
Firefighters think work being done on some equipment inside the building may have sparked the fire.
The building -- made mostly of concrete -- was used to store tractors and other equipment for the prison facility off Spurr Road.
The fire broke out around 6 a.m.
It's not believed to be suspicious.
Firefighters plan to spend time Monday investigating the cause.