Knoxville, TN (WOKI) A cigarette butt is to blame for a fire over Mother’s Day weekend at a Knoxville apartment building.

That, according to Knoxville Fire Department officials Thursday who say investigators determined the May 10 fire at Spring Meadow Apartments is the result of someone discarding the cigarette in a flower pot on the exterior balcony of the building.

“Although a flower pot might seem harmless, a single smoldering cigarette can turn its contents into a slow-burning fuse,” said Assistant Chief Mark Wilbanks. “Within minutes, that concealed heat can reach neighboring combustibles and erupt into open flame, as we saw last weekend.”

KFD officials say potting mixes are engineered to stay light and airy, making them perfect for catching fire.

More than 20 people were displaced last weekend due to the fire.