FALCONER — Spontaneous combustion of mineral oil-soaked cotton rags in a plastic garbage can caused heavy smoke to fill Falconer Central School early Thursday.

No damage was reported after a fire alarm was reported at the 220 East Ave. school around 1:30 a.m. Firefighters located the fire inside the custodian work shop area in the basement after encountering heavy smoke.

The fire was quickly extinguished, the Chautauqua County Sheriff’s Office said.

Fire investigators determined the fire originated in the work shop area and was due to spontaneous combustion.

Firefighters from several departments were called for assistance.