"It's burning up under the ground," he said. "You can see the smoke rising there."
To get at the fire underground, Fales said officials brought in a bulldozer to dig the tires out. Fales said the fire spewed thick, dark smoke.
"When we got here, the whole sky was black," he said.
Because the fire is about 100 yards from a creek, Fales said experts from the Maryland Department of Environment were alerted at about 9 p.m.
John Myers, an official with the department's Emergency Response Division, said Wednesday night that the creek did not appear in danger. But he said he would stay on the scene in case there were hazardous materials underneath the burning tires.
The tires initially were used to hold down a tarp over a pit that was used to hold feed for livestock.
"It's some kind of dump that we're not familiar with and we're not sure what might be underneath the tires," Myers said.
The fire may have been burning for up to two weeks, he said.
Myers said an inspector from the department's Solid Waste Program will inspect the area today to asses the damage, but he added that he does not expect any long-term effects.
Robert Harbaugh, who owns the property, said he returned from work Thursday afternoon and saw smoke coming from the pit. He said he was planning to kick dirt over it to put it out but discovered it was a much bigger problem.
Harbaugh, 62, who lives across the street at 20008 Millbrook Road, said he stopped farming about seven years ago. He said he intended to fill in the pit and remove the tires but had not gotten a chance to do it yet.
The number of tires involved in the fire was not clear Wednesday night. Fales said there probably were a couple hundred tires in the pit, but Harbaugh said he never had more than 50 there.
Tankers from Sharpsburg, Dargan, Middletown, Md. and the Washington County Air Unit assisted.