(AP) — Authorities have determined an improperly discarded cigarette caused an extensive apartment fire last week in southwest Omaha.

Assistant Fire Chief Dan Stolinski says a cigarette stubbed out in potting soil on a second-floor balcony deck reignited Friday at the Applewood Point apartment complex. The fire forced about 80 people to evacuate and took more than three hours to be extinguished.

The blaze caused the roof and portions of third- and second-floor ceilings to cave in. Batallion Chief Robb Gottsch says he doubts the structure can be saved.