Knoxville Fire Department crews were called back to the scene of Fort Loudon Waste and Recycling on Monday evening, after a flare-up started after workers charged with keeping watch over the facility left the premises.

Crews were summoned around 7 p.m. Fire officials say the facility had agreed to post a 24/7 fire watch, but the smoke appeared during the time the two watchers had left. And when they returned, the pair was said to be “shocked” to find firefighters on site.

Fire Department Captain DJ Corcoran said a propane-fueled forklift backfired last Wednesday, igniting several pallets of loose paper, sparking the blaze that burned two acres of the plant and took more than two full days to extinguish.

The heavy smoke and burning plastic necessitated the evacuation of some 100 nearby homes.