The building, owned by James and Julie Albert, of Hinton, suffered extensive structural damage, following the early morning fire, said Merrill Fire-Rescue Chief Bill Merchant.
The pole building was used as a storage and maintenance shop for Albert Trucking, owned by the Alberts.
Merchant said the fire most likely started in an oil burning stove's chimney and climbed into the ceiling rafters.
"A lot of big companies use waste oil burning stoves in their shops," Merchant said. "Most of the time they are pretty safe, but they do require regular cleaning and maintenance just like any chimney."
Fire burned in the rafters above an office area in the building, at 23517 Old Highway 75, damaging most of the front, or south, portion of the structure, Merchant said.
"All their trucking records, a laptop, all their papers -- everything they had in the office burned down to nothing," he said.
At the time of the fire, two trucks with trailers parked inside the pole building were not damaged by the flames, Merchant said.
"They just had a little smoke on them," he explained.
Merchant said he saw flames shooting from the metal building upon arriving at the Merrill Fire-Rescue station Monday morning.
The fire-damaged building is located directly behind the fire station, he said.
Firefighters extinguished the original blaze by about 8:30 a.m. Monday, but returned to the scene at 10:48 a.m. that day.
"I'd been watching the fire," Merchant said. "When it started smoking a little bit more, I called the fire department back."
Upon return, firefighters discovered fire in the insulation of the roof.
When firefighters sprayed the flames with water, Merchant said the entire ceiling of the building caved in.
"All the load bearing beams are pretty much burned out of it," he said. "The roof is bowed in the front half of the building. The tin is ruined on the building."
The 5,760-square-foot pole building was constructed in 1977, and remodeled in 2010, according to online property records from the Plymouth County Assessor's office.
Due to the structural damage to the building, Merchant said he considered it to be "pretty much shot."
The Merrill Fire-Rescue Department was assisted during the original 4:12 a.m. fire call by the Le Mars Fire-Rescue Department and the Hinton Fire Department.