Fire investigators have homed in on the cause of a fire that caused extensive damage to an unoccupied two-story building at the La Plata County Fairgrounds.

The fire was reported about 10:45 p.m. Friday in a building near the livestock pavilion, toward the back of the fairgrounds at 2500 Main Ave., prompting a robust response from Durango Fire Protection District with three engines and three medic units.

The fire, officials say, was contained by 11 p.m., though crews remained on scene late into the night.

Fire Marshal Karola Hanks said from the outset that no foul play was suspected.

On Wednesday, Hanks said fire investigators nailed down one of two causes, both related.

Hanks said a floor fan had been placed on the second story of the building to dry out a leak. Investigators believe the cord connecting the fan to the electric outlet or the fan itself overheated, causing the fire.

To pin down a more definitive cause, Hanks said samples would have to be sent to a lab. However, she said the decision to do that is up to the insurance company. She added the cost of damages is being determined.

The fire destroyed the second floor of the building, which will require an extensive demolition and rebuild. The lower part is salvageable, Hanks said, but the structure as a whole – which has bathrooms, offices and storage space – is currently unusable.

Hanks said the structure over the nearby pavilion and horse arena was not damaged.

“That’s a good thing,” she said.

jromeo@durangoherald.com