Firefighters from the Level and Darlington volunteer fire companies were among about 60 firefighters who responded to the 400 block of Connelly Road after a fire was reported at 4:08 p.m., according to the Maryland State Fire Marshal's office and fire company Facebook pages.
No one was injured in the fire, which took an hour to control, according to the notice of investigation from the Fire Marshal's Office.
The two-alarm fire was discovered by the property owner and caused about $50,000 of total damage, according to the notice of investigation.
Other companies that responded were from Port Deposit, Rising Sun, as well as Lancaster County, Robert Fulton Township, Chester, Oxford and Cochranville in Pennsylvania, according to the Fire Marshal's Office.
Calls for manpower, equipment and backup were broadcast over Harford County emergency channels for more than an hour after the fire was first reported.
Level sent a tanker and two engines to the fire, according to a post on the company's Facebook page, which also said those units were on scene for about three hours.
The cause of the fire has not been determined, according to the notice of investigation.
The wood-and-metal barn "was used to store hay bales and feed," according to the Fire Marshal's Office.
"Due to the amount of fire damage, several ignition sources could not be ruled out," the notice of investigation states. "The investigation into the origin and cause of the fire is ongoing."