LEWISBURG — A grain roasting machine that exploded into flames in Union County on Wednesday night engulfed the roof of a metal garage and caused about $121,000 in damage.

Doug Groff, son of the owner of Groff’s Grain Roasting, 262 Pawling Road, Kelly Township, said he did not know what caused the fire. He arrived at the scene right after a relative in a nearby house heard a pop as the fire started.

A grain roasting machine includes a long, hollow, rotating drum and a burner that produces a flame.

Gene Baker, White Deer Township fire chief, said he received notice of the fire at 9:12 p.m.

“By the time we got there the structure was well engulfed,” he said. “But once we got the hoses working, we put the fire out quickly.”

Baker said the fire started in the engine compartment of a 1999 Mack truck. Groff had just finished using the grain roaster, which is mounted on the truck.

“Then the relief valve of a 500-pound propane cylinder popped and that fueled the fire,” Baker said.

Baker estimated there was $75,000 in damage to the structure and $46,000 damage to the truck and grain roaster.

The fire was well under control by 10 p.m.

None of the assisting fire and rescue personnel from White Deer and Turbot townships, Milton and Lewisburg were injured. Milton fire police blocked off the road to traffic at about 9:15 p.m.