Oily rags and spontaneous combustion are blamed for a small fire that ignited inside a downtown store this morning, authorities said.

Butler firefighters quickly snuffed out the blaze shortly after 9 a.m. at Worsley’s Collectibles next to the Penn Theater on North Main Street.

No one was hurt but the damage was no paltry sum — as much as $35,000, said Fire Chief Nick Ban.

“We believe the fire was caused by oily stain rags that were thrown into a metal trash can,” Ban said. “The rags can spontaneously combust from the heat built up in the trash can.”

The trash can was on the second floor and it actually ignited the joist work between the first and second floors.

Firefighters had to rip up flooring between the floors to extinguish the fire.

The store had just opened for the day when smoke was reported on the second floor of the three-story building that also houses Worsley’s Dolls and Bears.

Ban said he and other firefighters found the smoldering trash can in the middle of the second floor, which is used for a furniture finishing area.

Butler police blocked traffic on North Main Street between North and West New Castle streets. The street opened about 10:30 a.m.