The fire destroyed the management offices of Abilene Machine, which makes aftermarket parts for farm equipment.
The safe was discovered in the burned-out accounting office by a cleanup crew, Dickinson County Undersheriff John Nachtman said. He said it was not clear what might have been taken.
``Everything pretty much burned up in the safe,'' he said.
Dan Britt, chief of the Solomon and Lincoln Township volunteer fire department, said Wednesday the fire broke out in the accounting office.
``Someone definitely broke into the safe using a torch,'' Britt said. ``We don't know if it was arson, or if things just caught on fire while they were doing that.''
It took 40 to 50 firefighters about two hours to control the blaze, Britt said.
One reason for the lengthy battle, he said, was that the fire spread to a paper-filled loft.
``We lost half of the warehouse and half of the sales office,'' Britt said.
With about 110 workers, Abilene Machine is one of Dickinson County's largest employers. Despite the damage, telephone sales operations resumed Wednesday morning, officials said.
``It will probably be six or eight months until we are back to normal,'' said Dan Sexton, the company's purchasing manager.
