The start of school for a number of high school students in Green Bay, Wis., will be delayed until mid-September due to smoke damage from a fire that started after rags used to clean up a refinishing job spontaneously combusted in the middle of the night.

 Green Bay Metro Fire Lt. Nick Craig told local media at a press conference that school district employees put rags “used to clean up the refinishing product” in a garbage can lined with plastic that was sitting next to the gym’s bleachers. The rags combusted, starting the garbage can on fire.

The fire started at 1:20 a.m, Aug. 8, in the Preble High School gymnasium. The video below comes from a security camera in the gymnasium, and captures the fire as it began.

The local fire department was able to contain the fire in the area, but the rest of school received heavy smoke damage. The school will remain closed until Sept. 15.

The same thing happened a year ago at a high school in Waukesha, Wis.

Take it from HF blogger Wayne Lee, who has seen two fires start due to spontaneous combustion while working on wood floors: "I cannot tell you the seriousness of spontaneous combustion." His video blog post on the topic is here.