LOUDOUN COUNTY, Va. (WRIC) — The culprit behind a fire that caused half a million in damages after destroying a barn belonging to northern Virginia homeowners was the spontaneous combustion of mulch and potting soil in a flowerbox, Loudoun County said.

“Spontaneous combustion can happen when a decomposing, organic material such as mulch generates enough heat to ignite without an outside source,” said System Chief Keith H. Johnson. “Because of this, a large or compacted area of mulch can create sufficient heat to spontaneously combust. Remember, in all cases, mulch fires are more likely to start when the weather is hot, and it has been dry for an extended period.”

Fire and emergency crews responded to the blaze just before 4:30 p.m. on Tuesday, Sept. 20. Hazardous Materials response units were called in to help with the situation after the emergency communications center learned that the flames were approaching several large propane tanks.

Crews arrived to find the 40’ x 80’ barn with significant smoke and fire showing. Crews were able to quickly extinguish the blaze and “remained on scene for an extended period extinguishing hot spots and assisting the Fire Marshal’s Office investigation.”

The damages to the barn and its contents are estimated at $532,000. There were no injuries to any people or animals in the fire.