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Chicago Fire Department detectives said spontaneous combustion from rags used to stain the floor of the choir pew is the mostly likely culprit.
Fair warning to all readers:
Leaving oil-soaked rags in a pile is ASKING for spontaneous combustion. The oil evaporates and so generates heat, which builds up and can erupt in a fire spontaneously, that is, without being lit by anyone or anything else.
The way to prevent this is to submerge the used rags in water, and CLOSE the lid of the water container, and put the container OUTSIDE in the open air.
In this case, about 5 minutes of diligent custodial work could have prevented the whole fire.
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